'-NRLF 


10 


PULSATION   OK  JELLYFISHES. 


sided,  will  remain  the  same  as  it  was  before  the  radiating  cuts  were 
made.  Moreover,  its  excited  rate,  due  to  being  lifted  out  of  water  and 
dropped  back,  remains  the  same  as  it  was  before  the  cuts  were  made. 
On  the  other  hand,  cuts  designed  to  successively  reduce  the  area  of  the 
sub-umbrella  tissue  enervated  by  a  sense-organ  (such  as  are  shown  in 
fig.  2,  A  and  B)  usually  cause  the  normal  rate  of  pulsation  to  decline. 
The  excited  rates  >  however,  are  less  influenced  by  reduction  of  area, 
small  pieces  sometimes  pulsating  almost  as  rapidly  as  large  ones,  but 
the  duration  of  the  excitement  displayed  by  small  pieces  is  much 
reduced.  For  example,  in  the  A  series  of  figure  2 — 


Area. 

Normal  rate 
per  minute. 

Excited  rate 
per  minute. 

Al  . 

280 

Ao 

-1/ 

3* 

Ao  .. 

04 

5 

4U 

In  the  B  series  the  relative  areas  and  rates  were  as  follows : 


Area. 

Normal  rate 
per  minute. 

Excited  rate 
per  minute. 

Bi... 

271 

27 

CQ 

B?... 

I  ^"3 

14-20 

eg 

Bq... 

17 

48 

BA.. 

2 

14 

IQ 

B, 

JJ 

The  above  results  are  quite  similar  to  those  of  Romanes  uponAuretia, 
and  are  opposed  to  the  conclusion  of  Eimer  that  severed  portions  of  the 
disk  pulsate  at  rates  approximately  proportionate  to  their  respective 
areas. 

It  is  interesting  to  observe  that  if  we  stimulate  a  Medusa  into  pro- 
longed and  active  pulsation  at  an  "excited"  rate  and  then  cut  out  the 
marginal  sense-organs,  each  sense-organ,  together  with  the  piece  of 
tissue  attached  to  it,  instantly  subsides  into  a  slow  rate  of  pulsation, 
never  faster  than  the  average  unexcited  rate  of  the  entire  Medusa. 
Moreover,  these  pieces  with  sense-organs  attached  can  not  immediately 
be  stimulated  into  a  display  of.  excitement,  although  after  an  interval 
of  time  they  will  readily  respond  and  exhibit  an  excited  rate  com- 
mensurable with  that  of  the  perfect  Medusa.  As  we  have  seen,  the 
display  of  "excitement"  is  a  function  of  the  undifferentiated  tissue  of 
the  sub-umbrella,  and  it  appears  that  the  excited  rate  of  the  Medusa 
may  be  maintained  by  the  influence  of  the  general  sub -umbrella  tissue 


INTERDEPENDENCE  OF  SUB-UMBRELLA  AND  SENSE-ORGANS.       II 

upon  the  sense-organs  even  after  the  sense-organs  have  become  too 
exhausted  to  themselves  maintain  an  "excited"  rate.  Moreover,  if 
we  stimulate  the  sub-umbrella  surface  by  touching  it  repeatedly  with  a 
crystal  of  K2SO4  the  disk  responds  by  active  contractions  and  forces 
the  sense-organs  to  respond  at  the  same  rate.  Then  after  the  stimu- 
lus is  withdrawn  the  sense-organs  are  found  to  have  been  exhausted 
by  the  contractions  of  the  disk  and  can  not  again  resume  pulsation 
until  after  a  long  interval  of  rest. 

Direct  evidence  showing  that  the  sub-umbrella  may  exert  a  control- 
ling influence  on  all  parts  of  the  sensory  tissues  of  the  Medusa  is  also 
afforded  by  the  following  experiment :  If  we  cut  off  the  basal  plate 
with  the  8  mouth-arms,  the  mouth-arms  remain  normally  expanded 
in  sea-water.  If  now  we  place  the  mouth-arms  in  a  solution  which 
resembles  sea- water,  but  lacks  potassium,  the  arms  contract  into  a 
close  bunch,  and  will  not  again  expand  as  long  as  they  remain  in  the 
solution.  If,  however,  we  place  a  perfect  Medusa  in  the  solution  it 
exhibits  periods  of  active  pulsation  alternating  with  periods  of  rest. 
Immediately  after  it  comes  to  rest  its  mouth -arms  contract  into  a 
close  bunch,  but  they  always  expand  again  as  soon  as  the  Medusa 
resumes  pulsation.  It  will  be  remembered  that  Romanes  showed 
that  removal  of  the  margin  of  the  bell  in  Sarsia  caused  the  manu- 
brium  to  elongate  and  lose  its  muscular  tonus.  He  also  found  that 
in  Sarsia  stimulation  of  the  sub-umbrella  caused  the  manubrium  to 
contract,  and  that  the  manubrium  of  Tiaropsis  indicans  would  apply 
its  mouth  to  any  stimulated  part  of  the  sub-umbrella,  provided  the 
stimulus  could  travel  radially  inward  from  the  stimulated  spot  to  the 
manubrium.  Otherwise  the  manubrium  executed  ill-directed  or 
wandering  movements. 

We  will  soon  show  that  any  difference  between  the  physiological 
action  of  the  marginal  sense-organs  and  that  of  the  general  sensory 
tissue  of  the  sub-umbrella  is  one  of  degree,  not  of  kind. 

CONTROL  OVER  PULSATION  EXERCISED   BY  THE  MARGINAL 
SENSE-ORGANS. 

Romanes  found  that  the  potency  of  the  marginal  sense-organ  attached 
to  a  segment  of  the  disk  has  more  to  do  with  its  rate  of  pulsation  than 
has  the  size  of  the  segment;  nevertheless  small  segments  usually  pul- 
sate slower  than  large  ones. 

In  Cassiopea  xamachana  there  are  13  to  23  marginal  sense-organs, 
and  I  find  that  the  average  rate  of  the  perfect  Medusa  is  apt  to  be  the 
same  as  the  rate  of  its  most  rapidly  working  sense-organ .  As  Romanes 
saw  in  Aurelia,  the  sense-organs  tend  to  initiate  stimuli  at  various 


wiwM^^^^ 


UNIVERSITY  OF 
DAVIS 


RHYTHMICAL  PULSATION  IN 
SCYPHOMEDUS^E 


BY 
ALFRED   G.  MAYER 

Director  of  Department  of  Marine  Biology  of  the 

Carnegie  Institution  of  Washington, 

Tortugas,  Florida 


WASHINGTON,  D.  C. 

Published  by  the  Carnegie  Institution  of  Washington 
1906 


CARNEGIE  INSTITUTION  OF  WASHINGTON 
PUBLICATION  No.  47 


FROM  THE   PRESS  OF 

THE  WILKENS-SHEIRY  PRINTING  CO 

WASHINGTON,  0.  C. 


RHYTHMICAL  PULSATION  IN  ANIMALS. 


1.  PULSATION  OF  JELLYFISHES,  ARMS  OF  LEPAS,  HEART  OF 
SALPA  AND  OF  LOGGERHEAD  TURTLE. 


I.  CONCLUSIONS  NEW  TO  SCIENCE. 

1.  If  we  cut  off  the  marginal  sense-organs  of  the  scyphomedusa 
Cassiopea,  the  disk*  becomes  paralyzed  and  does  not  pulsate  in  sea- 
water.  The  disk  will  pulsate  in  sea-water,  however,  if  we  make  either 
a  single  ring  or  a  series  of  concentric  broken-ring-like  cuts  through 
the  muscular  tissue  of  the  sub-umbrella.  Then  upon  momentarily 
stimulating  the  disk  in  any  manner,  it  suddenly  springs  into  rapid, 
rhythmical  pulsation  so  regular  and  sustained  as  to  recall  the  move- 
ment of  clockwork. 

Pulsation  will  not  start  unless  the  disk  be  momentarily  stimulated, 
as  by  a  mechanical  or  electrical  shock  or  by  a  single  touch  with  a 
crystal  of  K2SO4,  but  once  started  it  continues  indefinitely  in  normal 
sea- water  without  further  external  stimulation. 

The  waves  of  pulsation  all  arise  from  the  stimulated  point,  and  the 
labyrinth  of  sub-umbrella  tissue  around  this  center  must  form  a  closed 
circuit .  It  is  not  necessary  that  the  cuts  through  the  sub-umbrella  tissue 
of  the  disk  be  concentric  circles,  for  any  shape  will  pulsate  which 
allows  contraction  waves  to  travel  through  tissue  forming  a  closed  cir- 
cuit from  the  stimulated  center  and  back  to  this  center.  When  each 
wave  returns  to  the  center  it  is  reinforced  and  again  sent  out  through 
the  circuit;  and  thus  the  center  sustains  the  pulsation. 

NOTE. — It  is  a  pleasure  to  express  my  gratitude  to  those  who  have  aided  me  in  the 
prosecution  of  this  research.  To  Prof.  H.  S.  Jennings  for  his  kindness  in  sending  to 
me  lists  of  the  coefficient  i  for  the  making  of  isotonic  solutions ;  to  Dr.  Leon  J. 
Cole  and  Dr.  Charles  Zeleny  for  important  suggestions  and  criticisms;  to  Mr.  Daven- 
port Hooker  for  collecting  Gonionemus  and  Dactylometra,  and  to  Prof.  H.  F.  Perkins 
for  aid  in  collecting  Cassioj>ea  at  Tortugas ;  to  Professors  Ulrich  Dahlgren  and  Edward 
L.  Mark  for  instruction  and  aid. 

*In  this  paper  the  term  "disk"  will  be  used  to  designate  Medusae  from  which  the 
marginal  sense-organs  have  been  excised  ;  while  the  term  ' '  Medusa ' '  will  designate  the 
normal  perfect  animal. 


2  PULSATION   OF  JELLYFISHES. 

The  pulsating  labyrinth  may  be  simplified  after  the  rhythmic  move- 
ment has  started,  by  cutting  parts  of  it  away,  or  cuts  may  be  made  in 
such  manner  as  to  increase  its  complexity.  Any  cut  which  breaks 
the  circuit,  however,  stops  the  wave  of  pulsation,  and  continuous 
movement  can  not  again  be  started. 

The  rate  of  pulsation  of  the  disk  is  fully  twice  as  fast  as  that  of  the 
normal  perfect  Medusa.  This  rate  remains  constant  in  the  pulsating 
disk,  and  when  pulsation  ceases  the  movement  stops  instantly,  never 
gradually.  The  rate  of  pulsation  in  disks  deprived  of  marginal  sense- 
organs  depends  not  upon  the  area  of  the  tissue  forming  the  circuit, 
but  only  upon  the  length  of  the  circuit.  Short  circuits  pulsate  more 
rapidly  than  do  long  ones.  In  this  respect  it  differs  from  the  con- 
trol normally  exercised  by  the  marginal  sense-organs ;  for  small  pieces 
of  tissue  with  a  marginal  sense-organ  attached  pulsate  slower  than 
large  ones.  Moreover,  when  a  sense-organ  is  present,  tissue  of  any 
shape  will  pulsate  even  if  its  shape  does  not  form  a  closed  circuit. 

The  disks  of  Aurelia  and  Dactylometra,  if  cut  as  described  above, 
will  pulsate  as  does  the  disk  of  Cassiopea. 

These  experiments  show  that  the  rhythmical  pulsation  in  Medusae 
must  arise  from  a  definite  center  or  centers,  but  this  center  may  be 
established  at  any  point  in  the  muscular  layer  of  the  sub-umbrella. 
Once  established  it  remains  at  a  fixed  point,  while  the  disk  continues 
to  pulsate.  Sustained  pulsation  in  disks  occurs  only  in  tissue  forming 
a  complete  circuit,  and  depends  upon  an  electric  transmission  of 
energy,  and  the  pulsation  is  self-sustaining  (i.e.,  sustained  by  internal 
stimuli)  once  it  be  started  by  an  external,  momentary  stimulus* 

2.  If  normal   perfect  Medusae  be  lifted  out  of  water  and   then 
thrown  back,  the   rate  and  amplitude   of  their  pulsation  suddenly 
increases.     Pulsating  disks  react  in  a  similar  manner,  but  in  their  case 
the  amplitude  only  increases,  the  rate  remaining  practically  constant. 
The  presence  of  marginal  sense-organs  is  therefore  not  necessary  for 
the  display  of  "excitement.  " 

3.  The  stimulus  which  causes  pulsation   is   transmitted   by  the 
diffuse  nervous  or  epithelial  elements  of  the  sub-umbrella.     Newly 
regenerated  sub-umbrella  tissue,  which  lacks  muscular  elements  and 
can  not  itself  contract,  will  still  serve  as  a   bridge  to  transmit  the 
stimulus  which  causes  contraction  in  muscular  tissue  attached  to  but 

*  Professor  W.  T.  Porter  (1897)  found  that  any  part  of  the  ventricle  of  the  mamma- 
lian heart  (heart  of  the  dog)  will  beat  for  hours  if  supplied  with  defibrinated  blood 
through  its  nutrient  artery.  Isolated  portions  of  the  heart  of  the  hag-fish  continue  to 
beat  rhythmically  for  hours  even  in  the  absence  of  nutrition.  (See  A.  J.  Carlson,  1905, 
Amer.  Journ.  Physiol.,  p.  220.) 


CONCLUSIONS   NEW  TO  SCIENCE.  3 

beyond  the  bridge.  In  this  connection,  Carlson  has  demonstrated 
that  the  stimulus  which  causes  the  pulsation  of  the  heart  of  Limulus 
is  nervous  in  nature. 

4.  The  paralyzed  disk  of  Cassiopea  is  stimulated  into  temporary 
pulsation  by  all  salts  of  potassium,  sodium,  lithium,  barium,  iodine, 
bromine,  platinum,  weak  acids  (hydrogen),  ammonia,  and  glycerin. 
Magnesium,  calcium,  strontium,  urea,  and  dextrose  do  not  stimulate 
the  disk,  and  produce  no  contraction. 

5.  The  sodium  chloride  of  the  sea-water  is  the  chief  stimulant  to 
pulsation  in  Cassiopea,  while  magnesium  is  the  chief  restrainer  of  pul- 
sation, and  counteracts  the  influence  of  the  sodium  chloride.      Thus 
Cassiopea  will  pulsate  in  a  pure  ^n  NaCl  solution  for  more  than  half 
an  hour,  but  usually  comes  to  rest  in  less  than  two  minutes  in  a  solu- 
tion containing  the  amounts  and  proportions  of  NaCl  and  magnesium 
found  in  sea-water. 

I  find  also  that  the  heart  ofSalpa  democratica,  the  branchial  arms  of 
Lepas,  and  the  heart  of  the  embryo  loggerhead  turtle  pulsate  actively 
in  solutions  containing  only  NaCl,  K,  and  Ca,  magnesium  being  absent. 
Magnesium  inhibits  pulsation  in  all  of  these  cases,  as  it  does  also  in 
Cassiopea. 

The  general  r61e  of  NaCl,  K,  and  Ca  in  all  of  the  above  cases  is  to 
combine  to  form  a  powerful  stimulant  producing  an  abnormally 
energetic  pulsation,  which,  however,  can  not  continue  indefinitely ;  and 
magnesium  is  necessary  to  control  and  reduce  this  stimulus  so  that 
the  pulsating  organ  is  merely  upon  the  threshold  of  stimulation. 

A  Ringer's  solution  is  an  optimum  combination  of  NaCl,  K,  and 
Ca,  and  is  only  a  stimulant,  not  an  inorganic  food,  as  has  been  com- 
monly assumed.  The  organism  must  in  time  become  exhausted  under 
the  influence  of  this  stimulant  unless  a  certain  proportion  of  magne- 
sium be  present  to  restrain  its  action.  Indeed,  Ringer's  solution  prob- 
ably acts  by  withdrawing  magnesium  ions  by  osmosis,  and  replacing 
them  by  a  stimulant  composed  of  salts  of  Na,  K,  and  Ca.  Mag- 
nesium is  therefore  a  most  important  element  in  controlling  and 
sustaining  pulsation.  If  magnesium  be  precipitated  in  the  pulsating 
Cassiopea,  the  NaCl,  K,  and  Ca  immediately  produce  a  violent  pulsa- 
tion which  soon  passes  into  sustained  tetanus,  and  all  movement  ceases 
in  cramp-like  contraction.* 

*Loeb,  J.  1906;  Journ.  Biological  Chemistry,  vol.  i,  p.  331  '.  finds  that  in  the  hydro- 
medusa  Polyorchis  the  mouth  and  tentacles  are  permanently  contracted  in  any  solu- 
tion which  lacks  magnesium  ;  and  that  magnesium  serves  to  relax  the  muscles  of  the 
bell,  thus  counteracting  the  tetanus  caused  by  other  constituents  of  the  sea-wate 
guaranteeing  the  relaxation  after  a  systole. 


4  PULSATION   OF  JELLYFISHES. 

The  calcium,  of  the  sea-water  assists  the  NaCl  to  resist  the  retarding 
effects  of  magnesium.  Thus  Cassiopea  will  pulsate  from  half  an  hour 
to  an  hour  in  a  solution  containing  the  amounts  and  proportions  of 
NaCl,  magnesium,  and  calcium  found  in  sea- water,  but  usually  ceases 
to  pulsate  in  less  than  two  minutes  in  a  solution  containing  only  the 
NaCl  and  magnesium. 

Unlike  calcium,  potassium  does  not  assist  the  NaCl  to  overcome  the 
stupefying  influence  of  the  magnesium*  Thus  Cassiopea  ceases  to 
pulsate  almost  as  quickly  in  a  solution  containing  NaCl,  magnesium, 
and  potassium  of  sea-water  as  it  does  in  a  solution  containing  only 
the  NaCl  and  magnesium. 

The  potassium  of  sea- water  serves,  however,  to  stimulate  pulsation 
in  connection  with  both  calcium  and  NaCl.  Thus  Cassiopea  pulsates 
only  from  20  to  120  minutes  and  at  about  a  normal  rate  in  NaCl 
+  K2SO4,  or  in  NaCl  +  KCl,  whereas  it  pulsates  for  more  than  three 
hours  at  fully  twice  its  normal  rate  in  NaCl  +  K2SO4  +  CaSO4,  or 
NaCl  +  KCl  +  CaCl2. 

We  see,  then,  that  the  NaCl,  K,  and  Ca  of  the  sea- water  unite  in 
stimulating  pulsation  and  in  resisting  the  stupefying  effect  of  the 
Mg.  All  four  salts  conjointly  produce,  in  sea-water,  an  indifferent,  or 
balanced,  fluid  which  neither  stimulates  nor  stupefies  the  disk  of  Cas- 
siopea, and  permits  a  recurring  internal  stimulus  to  produce  rhythmic 
movement. 

6.  Cassiopea  does  not  pulsate  when  its  marginal  sense-organs  are 
removed,  simply  because  the  sea- water  does  not  stimulate  it.  If  stimu- 
lated in  sea- water,  in  any  manner,  it  readily  pulsates.  This  is  also  true 
of  Gonionemus,  and  Loeb's  statement  that  both  the  K  and  Ca  of  sea- 
water  inhibit  pulsation  is  not  supported ;  for  the  center  of  Gonionemus 
will  pulsate  actively,  though  temporarily,  in  sea- water  whenever  it  is 
touched  by  a  crystal  of  any  potassium  salt,  or  otherwise  stimulated,  f 

On  the  other  hand,  the  disks  of  Aurelia  and  Dactylometra  begin  to 
pulsate  in  sea- water  in  a  few  minutes,  as  soon  as  they  recover  from 
the  shock  of  the  operation  resulting  in  the  loss  of  their  marginal  sense- 
organs.  Unlike  Cassiopea  and  Gonionemus,  both  Aurelia  and  Dactylo- 
metra are  weakly  stimulated  by  the  sea-water  as  a  whole  and  pulsate 
almost  immediately  after  the  removal  of  their  margins. 

*The  general  anesthetic  effect  of  magnesium  has  been  well  known  since  the  re- 
searches of  Tullberg,  1892  ;  Archiv.  Zool.  Exper.  et  Gen.,  Tome  x,  p.  n. 

f  As  a  matter  of  fact,  the  disk  of  Gonionemus  is  often  seen  to  give  isolated  pulsa- 
tions, at  irregular  intervals,  in  sea-water  without  apparent  external  stimulation.  (See 
Yerkes,  1902.) 


CONCUJSIONS  NEW  TO  SCIENCE.  c 

The  disk  of  Cassiopea  usually  pulsates  spontaneously  in  an  irregular 
manner,  immediately  after  the  removal  of  its  marginal  sense-organs, 
if  it  be  placed  in  a  solution  containing  NaCl,  NaCl  +  KCl,  NaCl  + 
CaCl2,  or  NaCl  +  KC1  +  CaCl2  in  the  amounts  and  proportions  found 
in  sea-water ;  but  it  will  not  pulsate  in  any  solution  which  contains 
magnesium. 

7.  The  central  disk  of  Cassiopea,  if  set  into  pulsation,  will  pulsate 
longer  than  an  hour  in  a  solution  resembling  sea-water  but  lacking 
calcium,  whereas  the  normal  perfect  Medusa,  or  parts  of  the  margin 
containing  sense-organs,  cease  to  pulsate  in  this  solution  in  less  than 
six  minutes.     The  marginal  sense-organs  can  not  send  forth  stimuli 
producing  contractions  unless  they  be  constantly  supplied  with  calcium 
from  the  sea -water,  whereas  the  sub-umbrella  tissue  of  the  disk  itself 
is  relatively  independent  of  the  calcium  of  the  sea-water. 

On  the  other  hand,  both  the  disk  and  the  perfect  Medusa  will  pul- 
sate in  sea- water  saturated  with  CaSO4. 

8.  The  normal  Cassiopea  Medusa  will  pulsate  fully  three  times  as 
long  in  a  solution  of  Na2SO4  containing  the  same  amount  of  sodium 
as  is  found  in  sea-water  as  it  will  in  a  solution  of  Na2SO4  isotonic 
with  sea- water.     This  indicates  that  the  amount  and  proportion  of 
sodium  in  the  sea-water  is  more  important  to  pulsation  than  is  its 
osmotic  property. 

9.  The  contractions  of  the  heart  of  the  loggerhead  turtle  are  con- 
ducted and  maintained  exclusively  by  the  thin  peripheral  muscular 
part  of  the  wall  of  the  heart,  the  thick  cavernated  tissue  of  the  heart 
being  passive.     Moreover,  the  outer  muscular  part  of  the  heart's  wall 
is  a  better  electrical  conductor  than  is  the  cavernated  tissue.     A  sim- 
ilar condition  is  seen  in  Cassiopea,  where  the  thin  sub-umbrella  tissue 
of  the  disk  is  the  only  part  which  conducts  and  maintains  the  stim- 
ulus for  pulsation,  and  is  a  better  electrical  conductor  than  is  the  thick 
gelatinous  substance  of  the  disk. 

10.  The  chief  results  of  the  paper  are  the  discovery  of  a  new  method 
of  restoring  pulsation  in  paralyzed  Medusae,  and  also  that  magnesium 
plays  a  most  important  role  in  restraining,  controlling,  and  prolonging 
pulsation  in  animal  organisms. 

In  Cassiopea  the  ectodermal,  epithelial,  or  diffuse  nervous  elements 
of  the  sub-umbrella  transmit  the  stimulus  which  produces  rhythmical 
contraction. 

Rhythmical  pulsation  can  be  maintained  only  when  a  stimulus  and 
an  inhibitor  counteract  one  another,  and  cause  the  organism  to  be 
upon  the  threshold  of  stimulation;  thus  permitting  weak  internal 
stimuli  to  promote  periodic  contractions. 


6  PULSATION   OF  JELLYFISHES. 

MINOR    CONCLUSIONS. 

There  are  certain  minor  conclusions,  mainly  confirmations  or  am- 
plifications of  the  excellent  work  of  Romanes  upon  Scyphomedusse. 

In  Cassiopea  the  sub-umbrella  and  mouth-arms  are  the  only  parts 
which  respond  to  mechanical  or  chemical  stimuli.  The  ex-umbrella  is 
wholly  insensitive. 

There  is  no  essential  difference  in  kind  between  the  physiological 
action  of  the  sense-organs,  in  pulsation,  and  that  of  any  other  part  of 
the  sub-umbrella. 

Cassiopea  will  live  for  more  than  a  month  in  absolute  darkness. 
Its  plant  cells  then  degenerate,  but  the  Medusa  does  not  suffer;  hence 
its  vitality  is  not  dependent  upon  the  commensal  plant  cells  within 
its  tissues. 

Starved  Medusse  will  shrink  to  about  one-sixteenth  their  initial 
volume  and  still  survive.  They  will  live  in  brackish  water  contain- 
ing 75  per  cent  fresh  water  better  than  they  will  if  we  maintain  the 
amounts  and  proportions  of  calcium  and  potassium,  merely  reducing 
the  amounts  of  NaCl  and  magnesium  of  the  sea -water. 

The  fluids  of  the  gastro-vascular  space  and  of  the  body  of  the 
Medusa  are  only  slightly  alkaline,  while  the  sea- water  at  Tortugas 
is  decidedly  alkaline. 

The  sense-organs  tend  to  send  out  contraction  stimuli  at  various 
rates,  but  the  fastest  working  sense-organ  controls  the  Medusa. 

Excitement  of  the  disk  forces  the  sense-organs  to  maintain  a  higher 
rate  of  pulsation  than  they  are  capable  of  maintaining  if  cut  off, 
and  it  is  evident,  from  other  experiments,  that  the  disk  reacts  recipro- 
cally upon  the  sense-organs,  stimulating  them  into  activity. 

Small  pieces  of  the  disk,  enervated  by  sense-organs,  pulsate  slower 
than  large  ones. 

SmsdljyoUhg  Medusae  pulsate  faster  than  large  old  ones. 

The  sub-umbrella  surface  of  the  disk  exercises  a  reflex  control  over 
both  sense-organs  and  mouth-arms. 

Repeated  stimulation  of  any  one  part  of  the  disk  finally  tires  the 
stimulated  place  so  that  it  ceases  to  respond.  Other  parts  of  the  disk 
still  respond  as  readily  as  did  the  tired  place  in  the  first  instance. 

Having  stated  the  principal  conclusions,  we  will  now  proceed  to 
give  a  detailed  account  of  the  experiments  upon  Cassiopea,  Lepas, 
Salpa,  and  the  loggerhead  turtle. 


PLATE    1 


Aboral  views  of  Cassiopea  xamachana  Bigelow.     From  life.     Natural  size. 

Above,  rare,  small  variety.     This  bears  a  close  superficial  resemblance  to  the  common  Cassiopea  ndrosia  of  the  Fiji  Islands. 

(See  Agassiz  and  Mayer,  1899.  Bull.  Mus.  Comp.  Zool.  at  Harvard  Coll..  vol.  32,  p.  175,  pi.  14.) 
Below,  the  common  variety. 


NORMAL  MOVEMENTS   IN   SEA-WATER.  7 

II.     PULSATION  OF  CASSIOPEA  IN  SEA-WATER. 
INTRODUCTION— NORM AI,  MOVEMENTS. 

The  rhizostomous  Scyphomedusa  Cassiopea  xamachana  (plates  I, 
n),  is  very  abundant  during  spring  and  summer  in  the  salt-water  moat 
of  Fort  Jefferson,  at  Tortugas,  Florida.  It  was  described  by  Bigelow 
(1892,  1900)  from  a  salt-water  lagoon  in  Jamaica,  and  also  under  the 
name  of  Cassiopea  frondosa  by  Fewkes  (1883),  who  found  it  at  the 
Tortugas. 

The  Medusae  are  usually  found  gathered  in  clusters  upon  the  weedy 
bottom  of  the  moat  in  water  about  four  feet  deep.  They  lie  with  the 
aboral  side  of  the  disk  pressed  downward  upon  the  bottom,  and  with 
the  8  mouth-arms,  with  their  numerous  suctorial  mouths,  spread  out 
above.  A  sucker-like  concavity  on  the  aboral  side  of  the  disk  allows 
the  Medusa  to  adhere  with  considerable  strength  to  the  bottom  or  sides 
of  an  aquarium,  and  the  tenacity  of  its  hold  is  still  further  enhanced 
by  the  rhythmical  movement  of  the  disk,  which  beats  with  considerable 
regularity,  thus  tending  to  hold  the  bell  firmly  against  its  fastening, 
and  also  to  drive  a  current  of  water  out  over  the  mouth-arms. 

If  moved  from  its  normal  position  and  placed  in  the  water  with  its 
disk  uppermost  and  arms  downward,  the  rhythmical  beating  of  the 
disk  causes  it  to  swim  upward,  but  if  the  water  be  of  considerable 
depth  it  soon  topples  over  and  thus  swims  downward  to  the  bottom 
or  reaches  the  side  of  the  aquarium.  If,  however,  it  should  reach  the 
surface,  the  concavity  at  the  center  of  the  aboral  side  of  the  disk  often 
serves  to  permit  the  surface  tension  to  hold  the  Medusa  upon  the  sur- 
face, where  it  may  float  for  a  long  time,  pulsating  normally  with  the 
concavity  relatively  dry,  although  lower  than  the  general  surface  of 
the  water. 

The  Medusa  pulsates  with  a  regular  rhythmical  movement,  pauses  or 
irregularities  in  the  rhythm  being  exceptional.  Occasionally,  how- 
ever, its  rate  suddenly  increases,  with  or  without  apparent  cause,  and 
the  pulsation  may  become  so  active  as  to  cause  the  Medusa  to  break 
away  from  its  anchorage  and  glide  over  the  bottom.  A  regular  unex- 
cited  movement  is,  however,  often  maintained  for  hours  at  a  time,  and 
in  general  this  rate  of  pulsation  is  faster  in  small  than  in  large  Medu- 
sae, as  will  appear  from  table  i,  on  page  8. 

The  relatively  rapid  rate  of  small  Medusae  is  probably  due  to  their 
being  young  and  possessed  of  more  vitality  than  are  the  large,  old 
animals ;  for  not  only  do  small  Medusae  regenerate  lost  parts  more 
readily,  but  we  also  find  that  specimens  which  have  become  reduced 
in  size  through  starvation  pulsate  at  a  slower  rate  than  young  and 


8 


PULSATION   OF  JELIvYFlSHES. 


well-fed  Medusae  of  the  same  size.  Thus  one  Cassiopea  was  starved 
for  three  months,  and  the  diameter  of  its  disk  shrank  from  78  to  21 
millimeters,  while  at  the  same  time  its  rate  of  pulsation  declined  from 
about  40  to  1 6  per  minute.  It  is  also  interesting  to  observe  that  if 
we  cut  off  the  margins  of  the  disks  of  Medusae  of  various  sizes,  the 
severed  rims  of  the  small  Medusae  pulsate  at  a  more  rapid  rate  than 
do  those  of  the  large  Medusae,  although  in  both  cases  this  rate  is 
slower  than  that  of  the  uninjured  Medusa. 

TABLE  I. — Relation  between  the  rates   of  pulsation  and  the  diameters  of  the 
disks  in  Medusce  of  Cassiopea  xamachana. 


Diameter  of 
Medusa  in 
millimeters. 

No.  of  pulsa- 
tions per 
minute. 

Diameter  of 
Medusa  in 
millimeters. 

No.  of  pulsa- 
tions per 
minute. 

Diameter  of 
Medusa  in 
millimeters. 

No.  of  pulsa- 
tions per 
minute. 

13 

78 

28 

39-55 

62 

29 

15 

82-86 

28.5 

16-23 

63 

35 

16 

94-1  i  i 

30 

53-63 

82 

40-50 

18 

68 

31 

55-6i 

84 

28-39 

20 

36 

32 

58-62 

90 

16-28 

20.5 

45-65 

36 

42 

102 

2O-2I 

22 

60 

42 

51-54 

107 

23-24 

23 

44-71 

46 

45-46 

118 

7 

23-5 

40 

47 

43-36 

124 

12-16 

26 

43-52 

50 

27 

136 

9-12 

27 

41-56 

57 

36-37 

153 

7 

EXCITKMBNT. 

As  we  have  said,  the  pulsating  Medusae  occasionally  exhibit  a  sud- 
den increase  in  their  rate  and  amplitude  of  pulsation  without  apparent 
cause.  This  can,  however,  be  invariably  brought  about  as  a  response 
to  any  stimulus,  such  as  a  water  current,  a  mechanical  shock,  or  the 
introduction  of  some  irritating  chemical  into  the  water.  When  lifted 
wholly  or  partially  out  of  water,  and  replaced,  the  Medusae  pulsate  at 
about  twice  their  normal  rate  for  two  or  three  minutes,  and  the  ampli- 
tude of  their  pulsations  is  also  increased.  Even  small  fragments  of 
the  disk  containing  a  marginal  sense-organ  will  usually  display  this 
excitement,  although  the  duration  of  the  period  of  excitement  is  shorter 
for  small  than  for  large  pieces,  and  their  rate  of  pulsation  slower. 

However,  the  presence  of  marginal  sense-organs  is  not  necessary  for 
this  "excitement,"  for,  as  we  shall  soon  show,  we  have  succeeded  in 
causing  disks  deprived  of  marginal  sense-organs  to  pulsate  constantly 
and  regularly  in  sea- water ;  and  if  such  disks  be  pinched  or  lifted  out 
of  water  or  otherwise  disturbed  the  amplitude  of  their  pulsations 
becomes  suddenly  increased,  while  the  rate  remains  practically  con- 
stant. In  normal  uninjured  Medusae  both  rate  and  amplitude  increase, 


NORMAL   MOVEMENTS   IN    SEA-WATER.  9 

but  as  we  shall  see,  disks  without  sense-organs  pulsate  at  the  maxi- 
mum rate  at  which  their  tissue  is  capable  of  transmitting  the  wave 
of  pulsation,  and  they  can  therefore  exhibit  "excitement"  only  by 
an  increase  in  amplitude. 

It  is  worthy  of  note  that  if  the  forceps  used  to  stimulate  the  Medusa 
be  made  to  seize  upon  only  a  small  area  of  tissue,  the  Medusa  will  not 
respond,  but  on  bringing  a  larger  area  between  the  forceps  the  response 
is  sudden  and  violent.  In  this  connection  it  will  be  recalled  that 
Romanes  showed  that  the  bell  of  Sarsia,  when  deprived  of  its  margin, 
will  respond  to  mechanical  shocks  by  pulsations,  each  stimulus  usually 
giving  rise  to  one  or  two  pulsations,  and  this  is  also  true  of  the  par- 
alyzed disk  of  Cassiopea.  We  must  conclude  that  the  presence  of 
marginal  sense-organs  is  not  necessary  for  the  display  of  that  sudden 
increase  in  activity  which  we  have  called  "excitement,"  and  that  this 
response  may  come  from  many  or  all  parts  of  the  undifferentiated  tissue 
of  the  sub-umbrella.* 


Fig.   i.  Fig-  2- 

Romanes  showed  that  in  Aurelia  annular  cuts  separating  the  margin 
from  the  center  of  the  disk  caused  the  rhythm  to  become  slower,  and  he 
was  led  to  suspect  (1885,  p.  163)  that  a  stimulus  of  an  afferent  character 
emanates  from  all  parts  of  the  sensory  surfaces  of  the  sub-umbrella 
to  the  marginal  sense-organs,  although  of  this  he  had  no  direct  proo 
I  think  we  can  prove  that  this  is  the  case  in  Cassiopea,  for  if  we 
off  all  but  one  marginal  sense-organ,  and  then  make  cuts  through 
the  sub-umbrella  tissue  (fig.  i)  radiating  outward  from  the  sense-organ 
and  therefore  not  interfering  with  any  stimulus  which  may  travel  by  tl 
shortest  path  from  any  point  in  the  disk  to  the  sense-organ,  ti 
rate  of  pulsation,  after  the  excitement  due  to  the  operation  h 

•It  is  interesting  to  observe  that  Bancroft  and  Esterly  (1903)  find  that  while  con- 
tractions normally  originate  from  the  ganglionated  ends  of  the  heart  of  dona,  they 
may  originate  from  any  other  region. 


10 


PULSATION   OF  JELLYFISHES. 


sided,  will  remain  the  same  as  it  was  before  the  radiating  cuts  were 
made.  Moreover,  its  excited  rate,  due  to  being  lifted  out  of  water  and 
dropped  back,  remains  the  same  as  it  was  before  the  cuts  were  made. 
On  the  other  hand,  cuts  designed  to  successively  reduce  the  area  of  the 
sub-umbrella  tissue  enervated  by  a  sense-organ  (such  as  are  shown  in 
fig.  2,  A  and  B)  usually  cause  the  normal  rate  of  pulsation  to  decline. 
The  excited  rates,  however,  are  less  influenced  by  reduction  of  area, 
small  pieces  sometimes  pulsating  almost  as  rapidly  as  large  ones,  but 
the  duration  of  the  excitement  displayed  by  small  pieces  is  much 
reduced.  For  example,  in  the  A  series  of  figure  2 — 


Area. 

Normal  rate 
per  minute. 

Excited  rate 
per  minute. 

Ai... 

280 

17 

02 

A*... 

12 

AO 

Aq... 

I 

6 

1  1 

In  the  B  series  the  relative  areas  and  rates  were  as  follows : 


Area. 

Normal  rate 
per  minute. 

Excited  rate 
per  minute. 

B, 

271 

B* 

Al  L 

Bo 

T7 

Ag 

BA 

2 

I  A 

IQ 

BR     . 

I 

I4—2O 

•3  e 

The  above  results  are  quite  similar  to  those  of  Romanes  uponAurelia, 
and  are  opposed  to  the  conclusion  of  Kimer  that  severed  portions  of  the 
disk  pulsate  at  rates  approximately  proportionate  to  their  respective 
areas. 

It  is  interesting  to  observe  that  if  we  stimulate  a  Medusa  into  pro- 
longed and  active  pulsation  at  an  "excited"  rate  and  then  cut  out  the 
marginal  sense-organs,  each  sense-organ,  together  with  the  piece  of 
tissue  attached  to  it,  instantly  subsides  into  a  slow  rate  of  pulsation, 
never  faster  than  the  average  unexcited  rate  of  the  entire  Medusa. 
Moreover,  these  pieces  with  sense-organs  attached  can  not  immediately 
be  stimulated  into  a  display  of.  excitement,  although  after  an  interval 
of  time  they  will  readily  respond  and  exhibit  an  excited  rate  com- 
mensurable with  that  of  the  perfect  Medusa.  As  we  have  seen,  the 
display  of  "excitement"  is  a  function  of  the  undiiferentiated  tissue  of 
the  sub-umbrella,  and  it  appears  that  the  excited  rate  of  the  Medusa 
may  be  maintained  by  the  influence  of  the  general  sub-umbrella  tissue 


INTERDEPENDENCE  OF  SUB-UMBRELLA  AND  SENSE-ORGANS.       1 1 

upon  the  sense-organs  even  after  the  sense-organs  have  become  too 
exhausted  to  themselves  maintain  an  "excited"  rate.  Moreover,  if 
we  stimulate  the  sub-umbrella  surface  by  touching  it  repeatedly  with  a 
crystal  of  K2SO4  the  disk  responds  by  active  contractions  and  forces 
the  sense-organs  to  respond  at  the  same  rate.  Then  after  the  stimu- 
lus is  withdrawn  the  sense-organs  are  found  to  have  been  exhausted 
by  the  contractions  of  the  disk  and  can  not  again  resume  pulsation 
until  after  a  long  interval  of  rest. 

Direct  evidence  showing  that  the  sub-umbrella  may  exert  a  control- 
ling influence  on  all  parts  of  the  sensory  tissues  of  the  Medusa  is  also 
afforded  by  the  following  experiment :  If  we  cut  off  the  basal  plate 
with  the  8  mouth-arms,  the  mouth-arms  remain  normally  expanded 
in  sea- water.  If  now  we  place  the  mouth-arms  in  a  solution  which 
resembles  sea- water,  but  lacks  potassium,  the  arms  contract  into  a 
close  bunch,  and  will  not  again  expand  as  long  as  they  remain  in  the 
solution.  If,  however,  we  place  a  perfect  Medusa  in  the  solution  it 
exhibits  periods  of  active  pulsation  alternating  with  periods  of  rest. 
Immediately  after  it  comes  to  rest  its  mouth -arms  contract  into  a 
close  bunch,  but  they  always  expand  again  as  soon  as  the  Medusa 
resumes  pulsation.  It  will  be  remembered  that  Romanes  showed 
that  removal  of  the  margin  of  the  bell  in  Sarsia  caused  the  manu- 
brium  to  elongate  and  lose  its  muscular  tonus.  He  also  found  that 
in  Sarsia  stimulation  of  the  sub-umbrella  caused  the  manubrium  to 
contract,  and  that  the  manubrium  of  Tiaropsis  indicans  would  apply 
its  mouth  to  any  stimulated  part  of  the  sub-umbrella,  provided  the 
stimulus  could  travel  radially  inward  from  the  stimulated  spot  to  the 
manubrium.  Otherwise  the  manubrium  executed  ill-directed  or 
wandering  movements. 

We  will  soon  show  that  any  difference  between  the  physiological 
action  of  the  marginal  sense-organs  and  that  of  the  general  sensory 
tissue  of  the  sub-umbrella  is  one  of  degree,  not  of  kind. 

CONTROL  OVER  PULSATION  EXERCISED  BY  THE  MARGINAL 
SENSE-ORGANS. 

Romanes  found  that  the  potency  of  the  marginal  sense-organ  attached 
to  a  segment  of  the  disk  has  more  to  do  with  its  rate  of  pulsation  than 
has  the  size  of  the  segment;  nevertheless  small  segments  usually  pul- 
sate slower  than  large  ones. 

In  Cassiopea  xamachana  there  are  13  to  23  marginal  sense-organs, 
and  I  find  that  the  average  rate  of  the  perfect  Medusa  is  apt  to  be  the 
same  as  the  rate  of  its  most  rapidly  working  sense-organ .  As  Romanes 
saw  in  Aurelia,  the  sense-organs  tend  to  initiate  stimuli  at  various 


12  PUPATION   OF 

rates,  but  the  fastest  controls  all  the  others  and  forces  them  to  beat 
in  unison  with  it.  To  test  this,  I  took  a  Cassiopea  having  19  margi- 
nal sense-organs  and  a  normal  unexcited  rate  of  12  to  1 6  pulsations 
per  minute.  I  then  made  19  radial  cuts 
midway  between  the  19  sense-organs, 
so  as  to  divide  the  disk  into  19  practi- 
cally equal  sectors,  each  enervated  by  a 
single  sense-organ.  These  radial  cuts 
through  the  sub-umbrella  completely 
separated  the  sectors  one  from  another 
in  so  far  as  the  transmission  of  nervous 
impulses  were  concerned  (fig.  3).  Un- 
der these  conditions  one  of  the  sectors 
pulsated  18  times  per  minute  ;  2  pul- 
sated 17  times;  2  pulsated  16  times;  i  Fig.  3. 
pulsated  15  times;  3  pulsated  9  times  ;  i  pulsated  8  times;  4  pulsated 
7  times;  2  pulsated  6  times  ;  2  pulsated  5  times,  and  i  failed  to  pulsate. 
The  sense-organs  gradually  change  their  rates,  so  that  at  the  end  of 
an  hour  or  two  the  fastest  may  sink  to  second  or  third  place,  etc. 
Quite  often  one  or  more  of  the  sense-organs  either  failed  to  send  out 
pulsations  or  did  so  at  very  infrequent  intervals.  These  sense- 
organs  appeared  normal,  however,  and  if  stimulated  by  being  thrown 
into  sea -water  containing  i  per  cent  excess  of  K2So4  they  initiated 
pulsations  at  a  rapid  rate. 

As  Romanes  and  Eimer  showed,  if  we  cut  off  all  but  one  of  the  mar- 
ginal sense-organs  this  one  will  maintain  a  rhythmical  pulsation  of 
the  disk,  whereas  if  this  last  sense-organ  be  removed  the  disk  at  once 
becomes  more  or  less  paralyzed.  The  disks  of  Aurelia  or  of  Dactylo- 
metra,  however,  begin  to  pulsate  irregularly  a  few  minutes  after  the 
loss  of  the  last  marginal  sense-organ,  but  Cassiopea  remains  practi- 
cally paralyzed  for  about  24  hours  after  the  operation,  rarely  executing 
a  pulsation  unless  stimulated.  On  the  following  day,  however,  it 
occasionally  pulsates  without  apparent  stimulation,  and  three  days  after 
the  operation  the  disk  rarely  remains  for  a  minute  without  pulsating. 
The  pulsations  are, however,  isolated,  single,  and  separated  by  irregular 
intervals  of  time,  until  the  marginal  sense-organs  begin  to  regenerate. 
Romanes  showed  that  in  Hydromedusae  the  least  discernible  rem- 
nant of  the  bell-margin  if  left  intact  will  maintain  the  rhythmical 
movement  of  the  bell,  but  that  in  Scyphomedusse  the  marginal  sense- 
organs  are  the  only  parts  of  the  rim  which  normally  control  the 
rhythmical  pulsation.  I  find  that  if  one  cuts  off  the  tip  of  the  last 
remaining  sense-organ  of  Cassiopea^  thus  removing  the  otoliths  and 


CONTROL   OF  SENSE-ORGANS  OVER  PULSATION.  13 

pigment  spot  but  leaving  the  stalk  of  the  sense-organ  intact,  the  disk 
is  instantly  paralyzed.  Also,  when  the  marginal  sense-organ  regen- 
erates, regular  pulsation  is  resumed  as  soon  as  the  pigment  spot  and 
a  few  small  otoliths  begin  to  appear.  For  example,  figure  4  shows 
the  appearance  of  the  normal  sense-organ,  and  figure  5  the  condition 
of  a  regenerating  sense-organ  that  has  become  capable  of  control- 
ling the  rhythm  of  the  disk.  Immediately  after  death  the  pigment  of 
the  sense-organ  dissolves  out  into  the  sea-water ;  on  the  other  hand 
it  appears  remarkably  stable  in  the  living  animal,  and  is  not  faded  by 
the  most  intense  sunlight,  nor  changed  by  one  month's  confinement 
in  absolute  darkness. 


Fig.  4.  Fig'  5' 

Fig.  4.— Enlarged  views  of  a  sense-organ  of  a  mature  Medusa  of  Cassiopea.     A,  aboral 

view;  B,  side  view;  C,  oral  view. 
Fig.  5.— Enlarged  oral  view  of  a  regenerating  sense-organ,  showing  the  beginning  of  the 

formation  of  pigment  spot  and  otoliths.     A  wide  strip  of  new  tissue  (dotted)  separates 

the  sense-organ  from  the  old  muscular  layer  of  the  sub-umbrella. 

If  a  sense-organ  be  cut  out  with  the  merest  remnant  of  sub-umbrella 
tissue  left  attached  to  it,  examination  under  the  microscope  shows 
that  this  tissue  continues  to  pulsate  rhythmically,  and  it  is  apparent 
that  the  area  of  the  sub-umbrella  tissue  attached  to  a  sense-organ  may 
be  reduced  to  a  practical  zero  without  any  more  marked  effect  than  a 
not  very  pronounced  slowing  of  its  rate  of  pulsation.     On  the  other 
hand,  if  we  remove  all  but  one  of  the  sense-organs  and  then  place  the 
disk  in  sea-water  charged  with  CO2,  keeping  the  sense-organ  itself 
out  of  the  fluid,  the  disk  becomes  paralyzed  and  can  not  be  enervate 
into  contraction  by  the  sense-organ.     In  some  of  these  expenmen 
the  sense-organ  was  also  paralyzed,  although  it  had  not  been  : 
C02  solution.     In  others  the  sense-organ  continued  to  send  contrac- 
tions out  over  the  adjacent  tissue,  but  these  could  not  extend  ovei 
parts  of  the  sub-umbrella  which  were  bathed  by  the  CO2. 


14  PUI^ATION   OF  JELLYFISHES. 

All  experiments  serve  to  demonstrate  that  the  nervous  relation- 
ship between  the  sense-organs  and  the  general  sub-umbrella  tissue  is 
reciprocal,  as  has  been  clearly  shown  by  Romanes,  who  found  that  if 
we  cut  a  strip  of  tissue  from  the  disk  of  Aurelia,  leaving  a  sense-organ 
at  one  end,  and  then  gently  stroke  the  end  remote  from  the  sense-organ 
with  a  camel's  hair  brush,  the  marginal  sense-organ  at  the  other  end 
of  the  strip  will  be  stimulated  into  sending  a  contraction  wave  back 
over  the  strip  (Romanes,  1885,  pp.  74-77).  This  discharge  is  therefore 
of  a  reflex  nature.  Nagel  (1894)  supports  the  idea  that  the  marginal 
sense-organs  are  reflex  centers,  while  von  Uexkiill  (1901),  upon  evi- 
dence which  to  me  appears  insufficient,  concludes  that  the  marginal 
sense-organs  in  Rhizostoma  pulmo  are  merely  centers  for  the  reception 
of  mechanical  stimuli,  and  that  each  pulsation  of  the  bell  causes  the 
sense-organs  to  swing  to  and  fro,  and  this  stimulation  calls  forth  a 
new  pulsation. 

We  will  show  later  that  any  point  in  the  sub-umbrella  surface  may 
be  made  to  start  and  maintain  impulses  which  will  set  the  whole  disk 
into  sustained  and  perfectly  regular  rhythmical  pulsation.  There  is, 
therefore,  no  difference  of  kind  between  the  nervous  activities  of  the 
marginal  sense-organs  and  those  of  any  other  parts  of  the  sensory 
surface  of  the  sub-umbrella. 

As  to  the  function  of  the  otocysts  in  Hydromedusse,  Murbach  (1903) 
showed  that  in  Gonionemus  they  have  no  static  function,  for  if  they  be 
removed  the  normal  movements  of  the  Medusa  will  be  resumed  before 
they  are  regenerated.  Murbach 's  conclusion  that  the  seat  of  the  static 
function  is  "muscular  sensation  in  the  velum"  requires  confirmation. 
Injury  of  so  important  a  swimming  organ  as  the  velum  may  readily 
cause  irregularities  in  movements  by  abnormally  deflecting  the  water 
currents  passing  through  the  opening  of  the  velum  at  each  contrac- 
tion. Moreover,  Yerkes  (1902),  in  his  study  of  the  sensory  reactions 
of  Gonionemus,  found  that  the  velum  is  unaffected  by  stimuli  of  any 
sort. 

Romanes  (1885)  found  that  the  ocelli  of  Sarsia  and  Tiaropsis  are 
sensitive  to  light,  and  Yerkes  (1902)  demonstrated  that  the  tentacles 
of  Gonionemus  are  very  sensitive  to  chemical,  mechanical,  and  photic 
stimuli. 

The  rates  at  which  waves  of  contraction  travel  over  the  disk  in 
Cassiopea  range  from  150  to  1200  mm.  per  second,  each  individual 
displaying  a  characteristic  and  constant  rate.  Apparently  there  is  no 
relationship  between  the  size  of  the  Medusa  and  the  rate  of  trans- 
mission of  waves  over  its  sub -umbrella  tissue.  These  rates  were 


FUNCTIONS  OF  THE   MARGINAL  SENSE-ORGANS.  15 

determined  by  cutting  spiral  strips  reaching  from  the  margin  inward, 
in  the  manner  of  Romanes.  It  was  observed  that  when  the  spiral  was 
made  5  mm.  or  less  in  width  only  powerful  stimuli  would  travel  from 
one  end  of  the  strip  to  the  other,  and  if  under  these  conditions  a  single 
sense-organ  was  left  at  the  outer  end  of  the  strip,  waves  of  contraction 
which  started  from  this  sense-organ  might  or  might  not  reach  the  cen- 
tral part  of  the  disk.  If,  however,  the  end  containing  this  sense-organ 
were  touched  with  a  crystal  of  K2SO4,  or  any  other  potassium  salt,  a 
powerful  wave  of  contraction  immediately  ensued  and  always  traveled 
completely  through  the  spiral.  But  if  the  inner  end  of  the  spiral  were 
touched  with  the  crystal  of  potassium  salt,  not  only  did  the  wave  not 
always  reach  the  sense-organ,  but  it  traveled  only  three-quarters  as 
fast  as  did  the  waves  from  the  sense-organ.  When  the  sense-organ 
was  cut  off,  however,  the  waves  traveled  at  the  same  rate  from  either 
end  of  the  spiral  strip,  and  this  rate  was  the  slower  of  the  two  men- 
tioned above.  Evidently  the  sense-organ  reinforced  the  stimulus 
given  by  the  potassium  salt. 

In  this  connection  Romanes  showed  that  in  Aurelia  strong  stimuli 
may  initiate  waves  that  may  travel  over  the  disk  at  twice  the  rate  of 
weak  ones. 

Peripheral  parts  of  the  disk  transmit  stimuli  at  a  faster  rate  than  do 
parts  near  the  center  of  the  disk.  This  was  shown  by  Romanes  to  be 
the  case  in  Aurelia.  Altogether  the  outer  parts  of  the  sub-umbrella 
are  more  sensitive  than  the  inner. 

As  Romanes  showed,  there  must  be  an  appreciable  interval  of  rest 
between  two  successive  responses  to  stimuli,  and  rhythmical  waves 
can  not  follow  one  after  another  faster  than  a  certain  frequency. 
Waves  traveling  in  opposite  directions  through  the  same  strip  of  tissue 
meet  and  reinforce,  but  do  not  pass  each  other,  for  a  stimulus  can  not 
produce  a  contraction  over  the  tissue  that  has  been  in  contraction  only 
the  instant  before. 

The  sensory  field  of  the  Medusa  is  confined  to  the  sub-umbrella 
and  the  mouth-arms.  The  ex-umbrella  surface  exhibits  no  reactions 
to  stimuli,  and  indeed  the  epithelium  of  the  ex-umbrella  may  be  killed 
by  such  penetrating  reagents  as  Gilson's  fluid,  and,  provided  the  poi- 
sonous liquid  does  not  reach  the  sub-umbrella,  the  rhythmical  move- 
ment will  not  be  altered  in  rate.  Even  near  the  margin  of  the  disk 
close  to  the  sub-umbrella  surface,  the  ex-umbrella  is  inert  to  stimuli 
of  all  sorts.  The  action  of  the  sucker-like  concavity  at  the  aboral 
center  of  the  ex-umbrella  is  entirely  passive,  and  a  Medusa  deprived  of 
all  marginal  sense-organs  will  still  "cling"  to  the  bottom  or  side 
the  aquarium,  although  paralyzed  and  motionless. 


1 6  PULSATION   OF  JELLYFISHES. 

VITALITY,  ETC. 

The  fluids  of  the  central  stomach  of  Cassiopea  are  practically  neu- 
tral to  litmus  test,  whereas  the  sea- water  at  Tortugas  is  decidedly  alka- 
line. For  example,  litmus  paper  tinged  pink  by  HC1  is  changed  to 
blue  in  the  sea- water  in  from  9  to  12  minutes,  whereas  a  portion  of 
the  same  litmus  paper  thrust  into  the  central  stomach  cavity  of 
Cassiopea  will  not  become  blue  until  it  has  remained  in  the  stomach 
for  6  to  9  hours.  The  whole  surface  and  all  of  the  tissues  of  the 
Medusa  are  almost  neutral  and  much  less  alkaline  than  is  the  sea -water. 
The  stomach  cavity  may  be  filled  with  sea-water  charged  with  CO2» 
or  we  may  place  crystals  of  K2SO4  within  it,  and  }7et  little  or  no  effect 
will  be  produced  upon  the  movements  of  the  Medusa,  although,  as  we 
shall  see,  these  substances  produce  a  profound  effect  if  applied  to  the 
sub-umbrella  surface.  Remarkably  little  CO2  is  given  off  by  the 
Medusae  in  metabolism.  A  large  Medusa  was  confined  for  12  hours 
in  a  small  quantity  of  sea-water  tinged  pink  by  rosolic  acid,  and  the 
decoloration  of  the  fluid  was  barely  perceptible. 

Cassiopea  pulsates  regularly  and  at  its  usual  daylight  rate  through- 
out the  night,  and  even  red  light  has  no  apparent  effect  upon  its  rate 
of  movement.  If  long  confined  in  absolute  darkness,  however,  the 
rate  of  pulsation  becomes  slower,  and  the  plant  cells  within  the  tissues 
of  the  Medusa  become  shriveled  and  greatly  reduced  in  number,  so 
that  the  Medusa  becomes  pale  blue  in  color  and  translucent.  Only 
the  filaments  of  the  mouth-arms  retain  their  greenish  color.  (PI.  n, 
fig.  B.)  The  whole  color  of  the  Medusa  becomes  lighter  and  more 
uniform  than  the  normal,  as  will  be  seen  upon  comparing  figures  A 
and  B  of  plate  n.  Two  Medusae  of  Cassiopea  xamachana  were  main- 
tained in  absolute  darkness  and  without  food  for  one  month.  When 
first  placed  in  the  dark  their  diameters  were  82  and  42  mm.,  and  their 
rates  of  pulsation  40  to  50  and  51  to  54  per  minute,  respectively.  At 
the  end  of  one  month  the  large  Medusa  had  shrunken  so  as  to  be  but 
58  mm.  and  the  small  one  25  mm.  in  diameter,  and  their  rates  of  pul- 
sation 23  and  17  per  minute,  respectively.  On  their  being  removed 
to  the  diffused  daylight  of  the  laboratory,  the  color  remained  un- 
changed for  three  weeks,  but  the  diameters  of  the  Medusae  continued 
to  decrease;  finally,  however,  the  plant  cells  in  the  mid-region  of  the 
sub-umbrella  and  ex-umbrella  became  dark  brown  and  densely  crowded, 
so  that  these  parts  of  the  Medusae  were  dull  brown  in  color.  After 
being  in  the  light  for  one  month  the  large  Medusa  was  only  29  mm. 
in  diameter,  and  its  rate  of  pulsation  was  less  than  i  per  minute. 

On  the  other  hand,  when  the  Medusa  is  maintained  without  food  in 
the  light  it  becomes  dark  brown  in  color  (pi.  11,  fig.  c),  as  will  be 
seen  upon  comparing  its  photograph  with  that  of  a  normally  colored 


A.  Oral  view  of  a  normal,  recently  captured  specimen  of  Cassiopea  xamachana. 

B.  A  specimen  which  has  been  maintained  for  one  month  in  absolute  darkness,  showing  its 

pale  coloration.     The  plant  cells  are  much  reduced  in  number. 

C.  A  specimen  which  has  been  starved  for  one  month  in  the  light,  showing  its  very  dark 

brown  color. 


EFFECTS  OF  STARVATION,  AND  OF  DECREASED  SALINITY.     17 

Medusa.  The  greenish  color  of  the  oral  filaments  disappears,  and  the 
plant  cells  become  shriveled  and  densely  crowded.  A  Medusa  starved 
in  light  is  more  active  and  shrinks  more  rapidly  than  does  one  starved 
in  darkness,  and  thus  it  appears  that  metabolism  proceeds  more  rap- 
idly in  light  than  in  darkness.  For  example,  a  Medusa  starved  in 
diffused  daylight  had  a  diameter  at  the  beginning  of  the  experiment 
of  78  mm.  At  the  end  of  2  months  its  diameter  was  37  mm.,  and  at 
the  end  of  3  months,  21  mm.,  being  still  vigorous  and  pulsating  at  the 
rate  of  16  per  minute. 

These  starved  Medusae  exhibited  certain  phenomena  of  degenera- 
tion. The  mouth-arms  became  reduced  to  mere  stumps,  most  of  the 
mouths  closed  over,  and  the  oral  tentacles  and  filaments  were  absorbed 
or  cast  off,  so  that  the  oral  surfaces  of  the  mouth-arms  became  quite 
smooth  and  rounded.  The  marginal  lappets  of  the  disk  became 
blunted,  and  the  dull-white  peripheral  ring  of  the  ex-umbrella  was 
much  reduced  in  width.  Only  immature  eggs  were  found  in  the 
gonads  of  starving  Medusae.  It  appears  remarkable  that  the  first 
parts  to  degenerate  are  the  mouths  and  mouth-arms,  although  these 
are  the  most  important  to  the  organism  if  in  danger  of  starvation. 
The  marginal  sense-organs  remained  normal  in  size  and  appearance. 

Cassiopea  xamachana  lives  in  salt-water  lagoons  having  but  limited 
communication  with  the  sea,  and  it  is  therefore  not  surprising  that  it 
will  survive  considerable  alterations  of  salinity.  Fresh  water  (rain- 
water) is  quickly  fatal  to  the  Medusae,  for  they  shrivel  rapidly;  all 
pulsations  cease,  and  even  if  removed  to  salt  water  after  less  than  five 
minutes'  exposure  to  the  fresh,  recovery  is  very  slow.  On  the  other 
hand ,  if  every  night  and  morning  we  decrease  the  salt  and  increase 
the  fresh  water  5  per  cent,  the  Medusae  can  be  brought  into  a  mixture 
of  25  per  cent  sea -water  plus  75  per  cent  fresh  water,  and  still  sur- 
vive. Their  rates  of  pulsation  become  successively  slower  as  the  salt 
water  is  reduced. 

Thus,  two  Medusae  in  pure  sea- water  had  rates  of  pulsation  of  20  and 
60,  respectively  ;  in  60  per  cent  sea-water  plus  40  percent  fresh  water, 
1 8  and  1 8 ,  respectively ;  in  50  per  cent  sea-water  plus  50  per  cent  fresh 
water,  14  and  18,  respectively;  in  40  per  cent  sea- water  plus  60  per 
cent  fresh  water,  8  and  4,  respectively;  in  35  per  cent  sea-water  plus 
65  per  cent  fresh  water,  7  and  2,  respectively;  in  30  percent  sea-water 
plus  70  per  cent  fresh  water,  3  and  2,  respectively;  in  25  per  cent  sea- 
water  plus  75  per  cent  fresh  water,  3. 

The  small  Medusa  ceased  to  pulsate  in  75  per  cent  fresh  plus  25  per 
cent  sea -water,  and  its  sub-umbrella  surface  became  insensitive  to  the 
most  powerful  stimuli,  such  as  a  touch  of  a  crystal  of  KC1  or  K  SO4; 
yet  when  transferred  to  50  per  cent  fresh  plus  50  per  cent  sea  water  it 


1 8  PULSATION   OF  JKLLYFISHES. 

recovered  and  pulsated  at  the  rate  of  1 1  per  minute.  The  large  Medusa, 
which  pulsated  only  3  times  per  minute  in  25  per  cent  sea- water  plus 
75  per  cent  fresh  water,  revived  quickly  and  pulsated  18  times  per 
minute  in  50  per  cent  salt  plus  50  per  cent  fresh  water. 

If  instead  of  mixing  the  sea- water  with  distilled  water,  we  employ 
a  solution  of  fresh  water  containing  the  amounts  of  potassium  and 
calcium  found  in  the  sea- water,  the  Medusae  do  not  survive  as  well 
as  they  would  in  ordinary  brackish  water,  and  their  rates  of  pul- 
sation are  much  slower,  as  will  appear  from  the  following :  Three 
Medusae  in  pure  sea-water  had  rates  of  pulsation  of  about  60  per 
minute  ;  the  same  Medusae  in  55  per  cent  sea-water  plus  45  per  cent 
rain-water  containing  the  same  amounts  of  potassium  and  calcium 
as  sea-water,  pulsated  8  to  14  times  per  minute  ;  in  45  per  cent  sea- 
water  plus  55  per  cent  rain-water  containing  the  same  amounts  of 
potassium  and  calcium  as  sea- water,  they  pulsated  2  to  9  times  per 
minute;  in  40  per  cent  sea-water  plus  60  per  cent  rain-water  containing 
the  same  amounts  of  potassium  and  calcium  as  sea-water,  they  pul- 
sated i  to  6  times  per  minute;  in  35  per  cent  sea-water  plus  65  per  cent 
rain-water  containing  the  same  amounts  of  potassium  and  calcium  as 
sea -water,  they  pulsated  o  to  2  times  per  minute;  in  25  per  cent  sea- 
water  plus  75  per  cent  rain-water  containing  the  same  amounts  of 
potassium  and  calcium  as  sea- water,  two  dead,  one  pulsated  about 
once  every  10  minutes. 

Evidently  a  uniform  reduction  of  the  magnesium,  sodium,  potassium, 
and  calcium  is  less  injurious  than  a  reduction  of  the  sodium  chloride 
and  magnesium  alone.  As  Ringer,  Loeb,  and  others  have  shown, 
a  balance  in  the  proportions  of  the  constituents  of  the  sea-water  is  more 
important  than  the  presence  of  any  single  salt. 

As  might  be  expected  in  Medusae  living  in  shallow  lagoons,  where 
evaporation  is  great,  Cassiopea  will  withstand  a  considerable  concen- 
tration of  the  salt  water  ;  however,  Medusae  in  100  cc.  sea- water  plus 
i  gram  NaCl  will  survive  for  12  hours,  but  their  pulsation  becomes 
irregular,  although  on  the  average  of  about  normal  rate.  The  mouth- 
arms,  however,  are  strongly  contracted,  and  the  Medusa  exhibits 
alternate  periods  of  rest  and  activity  in  its  rhythmical  movements. 

Cassiopea  will  pulsate  normally  in  sea- water  saturated  with  CaSO4. 

As  will  be  apparent  from  the  above,  Cassiopea  xamachana  is  one  of 
the  hardiest  of  Scyphomedusae.  It  survives  for  months  in  aquaria 
with  but  ordinary  care,  and  exhibits  wonderful  recuperative  powers 
from  the  effects  of  poisons.  If  subjected  to  constant  shaking,  as  in  a 
floating  live-car,  it  does  not  thrive  as  well  as  in  stationary  aquaria 
where  the  water  is  not  so  pure. 


NATURE  OF  THE   PULSATION-STIMULUS. 


THE  NERVOUS  OR  EPITHELIAL  NATURE  OF  THE  STIMULUS  WHICH 
PRODUCES  CONTRACTIONS. 

If  the  sub-umbrella  be  injured  by  scraping  parts  of  it  away,  as  in 
figure  5A,  i,  or  if  the  margin  be  cut  off  as  in  figure  5A,  in,  the  removed 
parts  are  soon  partially  regenerated,  as  shown  in  the  dotted  areas,  but 
this  newly  regenerated  tissue  is  at  first  epithelial  in  character,  and 
lacks  muscular  elements.  It  therefore  can  not  contract,  yet  if  it  be 
touched  with  a  crystal  of  K2SO4,  or  otherwise  stimulated,  it  trans- 
mits the  stimulus  across  itself  to  the  adjacent  muscular  tissue  of  the 
sub-umbrella,  which  contracts  vigorously,  although  the  newly  regener- 
ated tissue  which  conducted  the  impulse  does  not  itself  contract.  This 


Fig.  5  A. — Newly  regenerated  sub-umbrella  tissue  which  lacks  muscular  elements, 
and  can  not  itself  contract,  can  still  transmit  the  stimulus  to  pulsate  to  normal 
tissue  adjacent  to  it.     In  fig.  5A,  II,  the  stimulus  crosses  areas  A  and  B,  which 
TV  do  not  contract,  while  C,  D,  and  S  contract  in  the  order  named.    In  fig.  5A,  IV, 

the  bridge  of  newly  regenerated  tissue  does  not  itself  contract,  but  serves  nevertheless  to  transmit  the 
stimulus  causing  contraction  in  E  and  F. 

can  best  be  demonstrated  by  making  the  newly  regenerated  tissue 
serve  as  a  bridge  connecting  two  pieces  of  uninjured  sub-umbrella 
tissue,  as  is  shown  in  figure  5A,  n,  or  5A,  iv.  Then,  upon  touching 
figure  5A,  n,  at  5*  with  a  crystal  of  K2SO4  or  other  stimulant,  a  con- 
traction wave  passes  from  5  through  B-D-A-C  ;  but  B  and  A,  being 
newly  regenerated  tissues  without  muscular  elements,  do  not  contract, 
although  the  stimulus  which  produces  contraction  passes  across  them. 
Similarly  in  figures  5A,  iv,  if  K,  which  is  normal  sub-umbrella  tissue, 
be  caused  to  contract,  every  contraction  is  followed  by  F,  although  the 
bridge  of  newly  regenerated  tissue  which  connects  them  does  not  con- 
tract. These  experiments  tend  to  show  that  the  stimulus  which  causes 
pulsation  is  transmitted  by  the  epithelial  or  nervous  elements  to  the 
muscular  elements,  and  not  primarily  by  the  muscular  elements  them- 
selves. I  have  examined  many  specimens  of  newly  regenerated  tissue 


20 


PUPATION   OF  JELLYFISHES. 


which  did  not  itself  contract,  and  yet  transmitted  the  impulse  which 
produced  contraction  in  muscular  tissue  attached  to  it,  and  there 
appear  to  be  no  muscular  elements  in  the  newly  regenerated  tissue, 
although  these  often  develop  later.  In  these  examinations  I  made 
use  of  intra  vitem  methylene  blue,  Retterer's  method,  Flemming's 
fluid  followed  by  Ehrlick's  acid  hematoxylin,  corrosive  sublimate 
followed  by  aqueous  carmine  stain,  and  Hermann's  fluid,  but  in  no 
case  could  I  find  muscular  elements  in  sections  of  the  newly  regener- 
ated tissue  which  appeared  to  be  a  simple  columnar  epithelium,  under- 
laid by  a  thin  nervous  net- work  (see  fig.  36).  The  muscle  fibrillse 
of  the  sub-umbrella  are  striate,  and  are  easily  demonstrated  by  any  of 
the  above  methods.* 

A  B 

act  ect  cct         C 


m, 


Figs.  A-C. — Cross-sections  of  the  sub-umbrella  of  Cassiopea. 
Fig.  D. — Surface  view  of  newly  regenerated  sub-umbrella 
tissue,  ect,  ectodermal  epithelium.  Q,  gelatinous  substance  of 
the  disk.  M,  muscle  fibers.  5,  basal  membrane. 


Figure  A  is  a  cross-section  of  the  normal  uninjured  sub-umbrella  of 
Cassiopea,  cut  across  the  trend  of  the  circular  muscle  fibers  ;  while  fig- 
ure B  is  a  cross-section  through  regenerated  sub-umbrella  epithelium 
which  has  grown  over  an  area  from  which  all  cellular  elements  had 
been  cut  away  about  40  hours  before.  This  newly  regenerated  tissue 
can  not  itself  contract  for,  as  yet,  it  lacks  muscular  elements ;  but  it 
will  nevertheless  transmit  the  stimulus  which  produces  contraction  in 

*Hesse  (1895)  finds  that  the  nerve  fibers  in  the  sub-umbrella  of  Rhizostoma  pulmo 
extend  in  all  directions,  but  are  mainly  grouped  in  clusters  extending  from  sense- 
organ  to  sense-organ.  Bethe  (1903)  finds  that  in  Rhizostoma  and  Cotylorhiza  the 
epithelium  of  the  sub-umbrella  is  connected  with  the  deep-lying  muscles  by  means  of 
an  intermediate  plexus  of  nerve  fibers. 


THE   PULSATION -STIMULUS   IS   NON-MUSCULAR.  21 

muscular  tissue  adjacent  to  it.  There  are  a  few  spindle-shaped  (gang- 
lion?) cells  upon  the  basal  membrane  at  the  base  of  the  regenerated 
epithelium,  and  occasionally  one  sees  a  large  rounded  cell  in  the 
gelatinous  substance  below  the  basal  membrane.  Occasionally  these 
rounded  cells  have  one  or  more  delicate  processes  which  extend  into 
the  gelatinous  substance. 

Figure  C  is  a  somewhat  slanting  section  through  regenerating  sub- 
umbrella  tissue  about  4  days  old,  which  is  beginning  to  regenerate  the 
muscle  fibers  and  can  now  contract  feebly.  The  muscle  fibers  appear 
as  elongate  processes  of  deep-lying  epithelial  cells,  and  extend  par- 
allel one  with  another  over  the  basal  membrane,  trending  circumfer- 
entially  around  the  sub-umbrella. 

Figure  D  is  a  surface  view  of  newly  regenerated  sub-umbrella  epi- 
thelium which  transmits  the  pulsation-stimulus,  but  can  not  yet  con- 
tract, as  it  still  lacks  muscular  elements. 

It  is  well  known  that  Carlson  has  demonstrated  the  nervous  nature 
of  the  stimulus  which  produces  pulsation  in  the  heart  of  Limulus. 
Indeed,  I  believe  that  all  of  the  facts  brought  to  light  by  Gaskell  in 
his  attempt  to  prove  the  muscular  nature  of  the  transmission  of  the 
stimulus  of  pulsation  in  the  vertebrate  heart  will  apply  equally  well  if 
we  assume  that  the  impulse  is  transmitted  by  diffuse  nervous  elements. 
In  the  heart  of  the  loggerhead  turtle  I  find  that  the  stimulus  causing 
pulsation  is  transmitted  entirely  through  the  thin  outer  muscular  part 
of  the  wall  of  the  heart,  and  the  thick  cavernated  inner  part  of  the 
heart's  wall  may  be  cut  away  without  affecting  the  pulsation.  Also, 
the  stimulus  to  pulsate  is  not  transmitted  through  this  cavernated 
tissue  to  the  muscular  tissue. 


Fig.  5B.— Showing  that  the  sub-um- 
brella tissue  is  a  better  electrical 
conductor  than  is  the  gelatinous 
substance  of  the  bell.  The  cur- 
rent travels  around  through  the 
long  way,  rather  than  across  the 
shallow  scratches  which  insulate 
the  area  B. 


The  sub-umbrella  tissue  of  Cassiopea  is  a  good  conductor  of  electri- 
city, while  the  gelatinous  substance  of  the  Medusa  is  a  poor  conductor. 
Thus  in  fig.  5  B,  if  we  insulate  an  annulus  by  the  shallowest  possible 
scratch  through  the  sub-umbrella,  and  then  isolate  a  small  sector, 
B,  by  shallow  radial  cuts ;  on  touching  the  large  sector  A  at  I  and  2 


22  PULSATION   OF  JELLYFISHES. 

with  the  electrodes  the  contraction  travels  all  the  distance  around  A , 
but  the  sector  B  does  not  contract.  The  path  of  least  electrical  resist- 
ance is  evidently  through  the  long  strip  of  sub -umbrella  tissue,  while 
the  short  path  across  the  cuts  interposes  a  greater  resistance. 

PULSATION  WITHOUT   MARGINAL  SENSE-ORGANS. 

Romanes,  Eimer,  von  Uexkiill,  and  others,  have  shown  that  in  Scy- 
phomedusse  the  marginal  sense-organs  are  centers  which  discharge" the 
stimuli  producing  the  rhythmical  movements  of  the  disk;  and  that 
if  we  remove  these  sense-organs,  a  more  or  less  complete  paralysis  of 
the  disk  occurs.  In  some  forms,  such  as  Aurelia  and  Dactylometra, 
this  paralysis  lasts  but  a  few  minutes,  and  then  more  or  less  irregular 
contractions  commence.  In  Rhizostoma  pulmo,  according  to  Hargitt, 
the  paralysis  is  much  more  pronounced  than  in  Aurelia.  In  Cassiopea 
xamachana  the  paralysis  is  practically  complete  for  at  least  24  hours, 
the  disk  responding  only  to  definite  stimuli,  and  very  rarely  giving 
a  contraction  without  evident  cause.  On  the  second  day  after  the 
operation  the  disk  is  much  more  sensitive  to  stimuli  of  all  sorts 
and  gives  occasional  isolated  contractions  without  apparent  stimu- 
lation, and  at  the  end  of  a  week  the  disk  can  rarely  be  observed  for  a 
minute  without  one's  seeing  it  give  a  number  of  quick,  isolated  contrac- 
tions. Regular  rhythmical  pulsation  never  sets  in,  however,  unless 
the  marginal  sense-organs  be  regenerated. 

Hitherto,  disks  without  sense-organs  have  always  been  maintained 
in  sustained  pulsation  by  constant  artificial  stimulation,  or  by  being 
placed  in  more  or  less  injurious  stimulating  solutions.  It  will  be 
recalled  that  Romanes  obtained  regular  pulsation  in  the  disks  of 
Aurelia  by  passing  through  them  a  constant,  or  faradaic,  current  of 
electricity  of  minimal  strength.  He  thus  demonstrated  that  rhythmi- 
cal movements  might  result  from  a  constant  stimulus,  and  he  showed 
that  one  contraction  could  not  follow  another  until  the  sub-umbrella 
tissue  had  recovered  from  the  exhaustion  caused  by  the  previous 
contraction  ;  then,  and  then  only,  can  the  tissue  respond  to  the  ever- 
present  stimulus.  Romanes  concluded,  therefore,  that  the  ganglia  of 
the  marginal  sense-organs  may  exert  a  constant  stimulus,  and  yet  give 
rise  to  periodic  contractions.  Romanes  also  found  that  the  paralyzed 
bell  of  Sarsia  could  be  set  into  a  "flurried  shivering"  pulsation  for 
one  hour  by  a  solution  of  10  to  20  drops  of  acetic  acid  in  1000  cc.  of 
sea- water,  and  that  it  would  also  respond  by  rhythmic  contractions 
to  a  solution  of  5  per  cent  glycerin  in  sea- water. 

In  1900  L/oeb  found  that  the  paralyzed  disk  of  Gonionemus  will 
pulsate  rhythmically  for  an  hour  in  a  solution  of  ^sn  NaCl  or  ^sn 


PULSATION   WITHOUT   MARGINAL  SENSE-ORGANS. 


NaBr,  but  that  a  small  amount  of  calcium  or  potassium  added  to  the 
Na  solution  will  prevent  the  disk  from  pulsating.  L/oeb  concluded 
that  the  calcium  and  potassium  ions  of  the  sea-water  prevented  the 
center  of  the  bell  of  Gonionemus  from  pulsating.  This  is  untrue  for 
Cassiopea,  for  not  only  will  the  disk  when  deprived  of  sense-organs 
pulsate  regularly  for  more  than  an  hour  in  an  artificial  sea-water 
without  calcium,  but  will  also  pulsate  indefinitely  in  natural  sea- 
water,  and  will  contract  rhythmically  in  solutions  containing  NaCl  + 
KC1,  or  NaCl  +  CaCl2,  or  NaCl  +  KC1  +  CaCl2  in  amounts  and  propor- 
tions found  in  sea- water.  All  solutions  containing  magnesium  tend 
to  prevent  pulsation  in  the  disk  of  Cassiopea. 

As  a  result  of  his  work  upon 
the  skeletal  muscles  in  1 899  Loeb 
concludes  that  rhythmical  con- 
tractions occur  only  in  solutions 
of  electrolytes,  i.  e.,  in  com- 
pounds capable  of  ionization, 
and  that  in  solutions  of  non-con- 
ductors such  as  glycerin  these 
rhythmical  contractions  are  im- 
possible. However,  Romanes 
found  that  glycerin  caused  rhyth- 
mical pulsation  in  Sarsia. 
Greene  (1898)  and  Howell(i9Oi, 
p.  189)  found  that  strips  of  heart 
muscle,  after  having  ceased  to 
pulsate  in  NaCl,  will  again  pul- 
sate if  immersed  in  a  pure  solu- 
tion of  cane  sugar  or  dextrose 
isotonic  with  the  NaCl  solution, 


and    I    find    that    the    heart 
Salpa  will   pulsate  normally  for 

more  than  half-an-hour  in  dex- 


p.g  6  _A  disk  o,  ^^  pressed  by  a  con_ 

of       centric  series  of  block-tin  rings  so  as  to  insulate 


circuits  of  tissue.     A  disk  so  pressed  may  be 

caused  to  pulsate  continuously. 
trose,  isotonic  with  sea-water  (see  table  6).      Thus  automatic  beats 
may  occur  in  a  solution  entirely  free  from  electrolytes,  but,  as  How- 
ell  shows,  these  beats  are  probably  dependent  upon  the  presence  of 
electrolytes  in  the  tissue  itself. 

When  we  come  to  consider  the  effect  of  ions,  etc.,  upon  Cassiopea,  it 
will  appear  that  one  must  be  cautious  of  drawing  general  conclusions, 
even  from  the  most  evident  effects  upon  any  one  animal.  Thus  I  find 
that  chemicals  which  produce  certain  perfectly  definite  and  invariable 
responses  upon  Cassiopea  act  differently  upon  Aurelia,  Dactylometra, 


PULSATION   OF 


Gonionemus,  Lepas,  Salpa,  and  the  loggerhead  turtle.  If  there  be 
marked  differences  between  the  reactions  of  closely  related  Scypho- 
medusse,  one  may  expect  even  greater  disparity  between  those  of  ver- 
tebrates as  compared  with  invertebrates. 

Roman es,L,oeb,  von  Uexkiill,  Hargitt,  and  others  have  caused  disks 
to  pulsate  temporarily  by  subjecting  them  to  the  influence  of  NaCl 
solutions,  etc.,  but  in  all  cases  more  or  less  toxic  effects  resulted  from 
the  experiments  and  the  sensibility  of  the  sub-umbrella  tissues 
became  impaired  or  destroyed,  so  that  further  stimulation  soon  became 
impossible.  We  will  now  describe  a  method  by  which  the  disk  of 
Cassiopea  when  deprived  of  marginal  sense-organs  may  be  made  to 
pulsate  indefinitely  in  sea-water  with  the  production  of  effects  no  more 
injurious  than  those  of  fatigue.  This  may  be  most  readily  accom- 


Fig.  7. — Oral  view  of  Cassio- 
pea xamachana.  Four  of 
the  mouth-arms  are  cut  off, 
and  the  muscle  layer  of  the 
sub- umbrella  in  the  upper 
right-hand  quadrant  removed 
to  show  the  underlying  vas- 
cular system.  ab,  Mouth- 
arm  plate;  ma,  mouth-arm; 
ml,  muscular  system  of  the 
sub-umbrella;  us,  vascular  ca- 
nals of  the  sub- umbrella. 


plished  by  cutting  off  all  marginal  sense-organs,  and  then  making  a 
series  of  concentric,  discontinuous,  ring-like  cuts  through  the  muscu- 
lar tissue  of  the  sub-umbrella,  as  is  shown  in  figures  8  to  19.*  Then 
upon  stimulating  the  disk  in  any  manner  it  instantly  springs  into  rapid 
rhythmic  pulsation,  so  regular  and  ceaseless  as  to  remind  one  of  the 
movement  of  clockwork.  The  cuts  must  be  so  made  as  to  permit 
a  free  passage  of  contraction  waves  through  sub-umbrella  tissue  form- 
ing a  closed  circuit.  The  simplest  circuit  is,  of  course,  a  single  ring 

*  A  glance  at  figure  7  will  show  that  the  muscular  area  of  the  sub-umbrella  is  a  wide 
annulus  with  the  mouth-arm  disk  and  stomach  in  the  center.  In  figures  8  to  33  we 
have  represented  the  disk  as  a  circle,  the  small  concentric  circle  at  the  center  being 
the  mouth-arm  disk,  while  the  wide  annulus  is  the  sub-umbrella. 


PULSATION   WITHOUT   MARGINAL  SENSE-ORGANS.  25 

(annulus)  of  sub-umbrella  tissue ;  and  such  a  ring  can  readily  be  set 
into  sustained  pulsation. 

It  is  not  necessary,  however,  that  cuts  be  made  through  the  sub- 
umbrella  tissue  ;  for  mere  pressure  prevents  the  transmission  of  con- 
traction waves  across  the  pressed  region,  and  we  may  form  circuits  by 
pressing  lightly  upon  the  sub-umbrella  with  a  concentric  series  of 
metallic  rings,  as  is  shown  in  figure  6.  Then  upon  stimulating  the 
disk  in  any  manner  it  pulsates  rhythmically. 

Disks  which  have  been  cut,  or  pressed,  as  described  above  do  not 
pulsate  until  they  have  been  momentarily  stimulated  at  some  definite 


Figs.  8-  19a,— Shapes  cut  from  disks  without  marginal  sense-organs.     These  will  pulsate 
continuously  in  sea-water. 

point  by  a  touch  of  some  potassium  or  sodium  salt,  a  mechanical  or 
electrical  shock,  or  by  suddenly  cutting  off  the  last  remaining  sense- 
organ  immediately  after  it  has  sent  out  its  contraction  wave. 

A  contraction  wave  travels  outward  from  the  stimulated  place 
through  the  circuit  of  sub-umbrella  tissue,  and  when  it  returns  to  the 
point  whence  it  started  it  is  immediately  reinforced,  and  again  sent 


PULSATION   OF  JKLLYFISHES. 


through  the  circuit.  Thus  there  is  normally  but  one  contraction  wave 
which  proceeds  from  its  center,  travels  through  the  labyrinth  of  sub- 
umbrella  tissue,  and  returns  to  the  center  whence  it  came,  only  to  be 
again  augmented  and  sent  forth. 

It  is  thus  the  function  of  the  center  to  reinforce  and  maintain  the 
contraction  wave.  This  is  well  shown  in  a  long  circuit  such  as  is 
shown  in  figure  30,  i-in ;  where  on  account  of  the  great  length  of 
the  circuit  the  course  of  the  wave  may  readily  be  followed  by  the  eye. 
The  outer  annuli  of  the  sub-umbrella  tissue  are  more  sensitive,  and 
conduct  contraction  waves  *  better  than  do  the  inner  parts  of  the  disk; 


27a 


26 


Figs.  20,  21,  22,  23,  25,  27a,  disks  cut  so  that  they  can  not  be  set  into  continuous  pulsation. 
Figs.  2 la,  23a,  24,  26  can  be  set  into  sustained  pulsation  in  sea- water. 

and  if  we  touch  the  disk  at  A,  figure  30,  i,  the  greater  part  of  the  con- 
traction wave  takes  the  short  path  of  least  resistance  into  the  interior  of 
the  labyrinth,  as  is  shown  by  the  full  arrow,  and  only  a  very  weak 
wave  goes  in  the  direction  of  the  dotted  arrow.  The  strong  contraction 

*  The  sub-umbrella  tissue  is  a  good  conductor  of  electricity,  but  the  gelatinous  sub- 
stance of  the  Medusa  is  a  poor  conductor. 


PUIvSATlON   WITHOUT   MARGINAL  SENSE-ORGANS.  2J 

wave  then  proceeds  as  is  shown  by  the  sequence  of  arrows  and  num- 
bers until  it  finally  returns  with  lowered  amplitude  to  the  center, 
where  it  is  instantly  restimulated  and  again  sent  through  the  circuit 
with  its  energy  restored.  The  same  conditions  apply  to  figures  31, 
ii  and  in. 

When  in  regular  pulsation  we  always  find  that  the  waves  of  contrac- 
tion start  from  a  definite  place.  The  position  of  this  center  tends  to 
bear  a  certain  relation  to  the  geometrical  figure  formed  by  the  cuts. 
It  is  marked  5  in  figs.  8  to  iga,  and  the  arrows  show  the  observed 
courses  of  the  wave  of  pulsation .  Usually  the  center  of  pulsation  lies 
near  the  periphery  of  the  disk  at  a  place  where  the  tissue  is  widest 
and  least  interfered  with  by  cuts,  and  it  also  tends  to  lie  upon  the  axis 
of  bilaterality  of  the  labyrinth  of  tissue. 

If  we  stimulate  the  disk  by  dropping  it  upon  a  glass  plate,  etc., 
the  waves  of  pulsation  start  from  the  point  5 ;  and  this  is  the  place 
where  we  must  touch  the  disk  if  we  wish  to  stimulate  it  into  sus- 
tained pulsation.  Wherever  we  touch  the  disk  with  a  crystal  of 
K2SO4,  waves  of  contraction  immediately  start  out  from  the  touched 
point,  but  it  is  usually  impossible  to  establish  a  permanent  center  of 


Fig.  28.  Fig.  29. 

pulsation  at  any  point  other  than  one  upon  the  geometrical  axis  of 
the  figure.  Centers  at  other  places  either  cease  to  initiate  pulsations 
when  the  effect  of  the  initial  stimulus  dies  out,  or  the  center 
quickly  shifts  to  the  geometrical  axis.  Sometimes,  however,  when 
a  disk  is  stimulated  by  a  severe  mechanical  shock,  two  or  more  per- 
manent centers  of  pulsation  appear  and  waves  of  contraction  start 
out  from  each  independently  and  interfere  where  the  opposing  waves 
meet  one  another.  Such  conditions  are  shown  in  figures  14  and  17. 

It  will  be  observed  that  with  the  exception  of  the  very  elongate 
spiral  (fig.  14)  all  of  the  labyrinths  formed  by  the  cuts  xtz  closed  circuits, 
the  tissue  being  merely  a  more  or  less  complicated  circuit,  with  the 
center  of  pulsation  at  the  geometrical  center  of  the  figure.  After  the 
disk  has  begun  to  pulsate  we  may  cut  away  portions  of  the  laby- 
rinth, and  the  part  containing  the  center  will  still  pulsate,  provided  it 
remains  a  closed  circuit.  Thus  the  crescent  (figure  i8a)  is  cut  out 
from  figure  18  and  the  ring  (figure  iga)  is  made  from  figure  19, 


28  PULSATION   OF  JKLLYFISHES. 

by  cutting  them  out  after  the  more  complicated  circuits  had  been  set 
into  pulsation.  Instead  of  simplifying  the  pulsating  labyrinth,  we 
may  increase  its  complexity,  but  as  long  as  the  waves  proceeding  from 
the  center  can  find  a  single  uninterrupted  circuit,  the  figure  pulsates. 
Thus,  a  disk  cut  as  in  figure  28,  A,  is  set  into  pulsation  and  then  all  of 
the  inner  rings  are  cut  so  as  to  be  converted  into  "cut-off"  paths  as 
in  figure  28,  B  ;  but  the  disk  continues  to  pulsate  until  we  cut  across 
the  outermost  ring,  when  it  stops  instantly.  Every  one  of  the  forms 
shown  in  figures  8  to  iga  can  be  thus  stopped  by  even  the  smallest 
cut  which  breaks  the  last  circuit,  although  they  continue  to  pulsate 
despite  any  cutting  which  does  not  sever  the  circuit.  Thus,  figure  16 
stops  at  once  if  we  cut  across  one  of  the  narrow  places  between  the 
rays  of  the  star. 

The  center  of  pulsation  usually  establishes  itself  in  a  large  uncut 
area,  but  once  it  be  established  we  may  greatly  cut  down  this  area 
and  not  interfere  with  the  center.  Thus,  the  ring  shown  in  figure  iga 
may  be  thinned  by  cutting  at  S,  but  the  center  remains  undisturbed. 


Fig.  30. — Very  elongate  circuits  showing  that  the  peripheral  parts  are  better  conductors  of  pul- 
sation than  are  the  inner  parts  of  he  sub-umbrella.  These  circuits  can  be  caused  to  pulsate 
continuously. 

Sustained  pulsation  without  marginal  sense-organs  can  be  main- 
tained only  in  tissue  forming  a  closed  circuit.  These  circuits  may  be 
complex  and  constricted  at  intervals  to  mere  thread-like  connectives, 
as  in  figures  31,  A-c,  where  every  annulus  is  crossed  by  radial  cuts  ;  or 
they  may  be  very  simple,  as  in  figure  31,  D.  The  circuits  may  either 
cross  or  trend  with  the  muscle  fibers.* 

On  two  occasions  disks  were  set  into  sustained  pulsation  when  only 
the  marginal  sense-organs  were  cut  away  ;  no  other  cuts  having  been 

*The  statement  in  my  preliminary  paper  in  the  Carnegie  Institution  Year  Book  for 
1905  that  the  circuits  must  trend  with  the  muscle  fibers  is  erroneous. 


PULSATION   WITHOUT   MARGINAL  SENSE-ORGANS. 


made.  This  can  rarely  be  accomplished,  however,  for  the  returning 
wave  must  usually  be  focused  back  upon  the  center  in  order  to  be 
sustained ;  and  in  a  wide  annulus  it  is  dissipated  and  returns  with 
too  little  force  to  call  forth  the  latent  ability  of  the  center  to  restimu- 
late  the  wave.  Similarly  figures  20,  21,  22,  23,  and  25  represent  forms 
which  dissipate  and  confuse  the  contraction  wave,  setting  up  "  eddy 
currents"  which  weaken  the  wave  and  prevent  its  returning  definitely 


Fig.  31. — A,  B,  and  C,  disks  having  every  annulus  crossed  by  radial  cuts,  but  which  may 
be  set  into  sustained  pulsation.  D,  a  simple  circuit  which  may  be  set  into  sustained 
pulsation. 

and  forcefully  to  the  center.  Hence  these  figures  can  not  be  set  into 
sustained  pulsation.  If,  however,  we  cut  partial  rings,  as  in  figures 
2ia  and  230,  or  convert  figure  21  into  a  shape  such  as  is  shown  in 
figure  24,  we  find  no  difficulty  in  setting  them  into  sustained  pulsa- 
tion. In  all  of  these  cases  the  figures  oblige  the  contraction  wave  to 
return  definitely  and  forcefully  to  the  center.  I  could  not  obtain  sus- 
tained pulsation  in  a  disk  cut  out  of  the  side  of  a  Medusa  as  in  figures 


30  PULSATION   OF  JELLYFISHES. 

27,  270.  This,  I  believe,  is  due  to  the  fact  that  the  contraction 
wave  returns  so  quickly  to  the  center  that  an  insufficient  time  elapses 
before  the  center  is  again  called  upon  to  restimulate  the  wave.  As 
Romanes  showed,  an  appreciable  interval  of  time  must  elapse  before 
tissue  which  has  been  in  contraction  can  again  contract. 

Very  elongate,  many-whorled  spirals,  such  as  one  sees  in  figure  14, 
are  the  only  forms  not  closed  circuits  that  we  have  succeeded  in  set- 
ting into  constant  pulsation.  This  occurs  only  when  two  or  more 
centers  arise  simultaneously  in  the  spiral,  as  in  S,  S',  and  S",  figure  14. 
These  centers  mutually  sustain  one  another,  the  contraction  wave  from 
one  being  restimulated  and  reflected  back  from  the  other.  If  one 
attempts  to  convert  a  series  of  partial  rings  (fig.  32,  A)  into  a  spiral 
by  successive  cuts,  as  shown  in  the  dotted  lines,  1-5,  (fig.  32,  B)  the 
tissue  ceases  to  pulsate  as  soon  as  the  final  cut  (5)  is  made  which 
breaks  the  last  circuit. 


A  B 

Fig.  32. — Showing  that  sub-umbrella  tissue  can  not  maintain  itself  in  pul- 
sation unless  it  has  the  shape  of  a  closed  circuit.  If  cuts  be  made  as 
shown  in  the  dotted  lines  in  the  order  1,  2,  3,  4,  5,  the  tissue  ceases  to 
pulsate  as  soon  as  cut  number  5  breaks  the  last  complete  circuit. 

It  must  be  borne  in  mind  that  cuts  through  the  sub-umbrella  tissue 
heal  over  in  the  course  of  a  day  or  two  and  will  then  transmit  pulsa- 
tion more  or  less  imperfectly  across  the  healed  lines,  and  then  a  spiral 
will  pulsate,  for  it  is,  physiologically  speaking,  only  a  series  of  concen- 
tric rings  of  readily  conducting  tissue  with  numerous  more  or  less 
imperfect  points  of  conduction  between  the  annuli.  Similarly  a  disk 
having  complete  circular  cuts  through  the  muscular  tissue  of  the  sub- 
umbrella,  such  as  is  shown  in  figure  26,  can  not  be  made  to  pulsate 
continuously  as  a  whole  until  two  or  three  days  after  the  operation, 
although  each  annulus  may  be  made  to  pulsate  independently.  After 
several  days  of  healing  the  cuts  will  allow  a  more  or  less  imperfect 
conduction  of  impulses  across  from  one  ring  to  another,  and  the  con- 


PULSATION   WITHOUT    MARGINAL   SENSE-ORGANS. 


traction  waves  will  be  unimpeded  circumferentially,  but  more  or  less 
hindered  radially.  That  this  is  the  true  explanation  of  the  matter  is 
proven  by  the  fact  that  the  disk  shown  in  figure  12,  wherein  the 
circumferential  cuts  are  numerous  and  the  spaces  between  are  as  wide 
as  the  cuts  are  long,  will  pulsate  continuously. 

Mere  mutilation  of  a  disk  without  sense-organs  will  not  cause  it  to 
become  capable  of  continuous  pulsation.  Thus  the  disk  shown  in 
figure  20,  having  about  800  punctures  made  through  its  sub-umbrella 
tissue,  can  not  be  set  into  a  sustained  rhythm. 

Although  I  had  several  hundred  paralyzed  disks  of  Cassiopea  capa- 
ble of  being  set  into  pulsation  by  a  stimulus,  such  as  a  momentary 
touch  of  a  crystal  of  K2SO4,  only  one  of  these  started  into  pulsation 
of  its  "own  accord."  Ordinarily  they  might  remain  for  days  in  the 
aquaria  awaiting  the  momentary  stimulus  which  alone  could  call  forth 
their  latent  power  of  rhythmical  pulsation. 

If  disks  without  marginal  sense-organs  be  set  into  rhythmical  pul- 
sation they  move  with  machine-like  regularity,  without  pauses,  and 
without  any  of  the  irregularities  shown  by  normal  Medusae  with  sense- 
organs  intact.  Their  rates  of  pulsation  are  not  only  practically  uni- 
form, but  they  are  much  faster  than  are  those  of  the  uninjured  normal 
Medusae  from  which  the  disks  were  prepared,  as  will  be  shown  by  the 
following  table : 

TABLE  2. — Rate  at  zvhich  normal  Medusce  of  Cassiopea  pulsated  and  the  rates  of 
pulsation  of  their  disks  zvhen  the  sense-organs  ivere  excised  and  circumferen- 
tial cuts  "were  made  in  the  sub-umbrella . 


Rate  of 

Figure 

pulsation  of 
the  normal 
Medusa  before 

Rate  of  pulsation  of  disk 
without  sense-organs. 

showing  the 
form  of  the 
cuts  made  in 

operation. 

the  disk. 

25-30 

77-88 

8 

32 

63-78 

9 

40 

183 

12 

51 

85 

13 

(  Outermost  center  S  .  .  117 

) 

15-20 

\  Mid-region  center  S'  .  101 
[  Innermost  center  S"  .     78 

[       '< 

(  Outermost  center.  .  .80-82 

i 

47 

1  inner  center  66-68 

i       7 

When  disks  without  sense-organs  are  set  into  pulsation  we  may  re- 
duce the  area  of  pulsating  tissue  by  cutting  parts  of  it  away,  but  the 
rate  of  pulsation  will  remain  constant,  provided  we  do  not  alter  the 
length  of  the  circuit  through  which  the  wave  must  pass.  If,  however, 
we  make  cuts  in  such  manner  as  to  increase  the  length  of  the  circuit 


PULSATION   OF  JELLYFISHES. 


the  rate  of  pulsation  becomes  slower.  For  example,  twenty  disks 
were  cut  as  shown  in  figure  33,  A,  and  after  they  had  been  set  into  pul- 
sation they  were  cut  across  as  shown  in  figure  33,  B.  This  cut  made 
the  circuit  twice  as  long  as  it  was  formerly,  and  obliged  the  contrac- 
tion wave  to  travel  double  the  distance  in  order  to  traverse  the  circuit. 


D 

Fig.  33. — Showing  how  cuts  may  be  made  so  as  to  increase  the  length  of 
the  pulsating  circuit,  thereby  decreasing  its  rate  of  pulsation. 

We  might  then  expect  the  pulsation  to  be  reduced  to  one-half  its  former 
rate,  but  as  a  matter  of  fact  the  wave  traveled  on  an  average  1.16 
times  as  fast  in  the  long  as  it  did  in  the  short  circuit,  so  that  the  cut 
reduced  the  rate  to  but  58  per  cent  of  its  former  value. 

Similarly,  if  we  set  disks  cut  as  shown  in  figure  33,  c,  into  pulsation, 
and  then  make  two  cuts  as  shown  in  figure  33,  D,  making  the  circuit 
almost  three  times  as  long  as  it  was  before,  the  rate  becomes  about 
0.4  of  its  former  value,  not  0.33  as  we  would  expect.  I  believe  that 
the  faster  rate  of  the  contraction  wave  in  the  long  circuit  is  due  to  the 
longer  rest  which  the  tissue  enjoys,  thus  allowing  it  the  more  com- 
pletely to  recover  and  regain  its  sensibility  to  the  stimulus  which 
calls  forth  the  contraction.  Romanes  showed  that  strong  contraction 


SENSE-ORGANS  AND   PUI^ATION.  33 

waves  travel  faster  than  weak  ones,  and  that  strong  stimuli  repeated 
at  short  intervals  soon  tired  the  tissue,  so  that  it  failed  to  respond. 

The  rate  of  pulsation  of  disks  is  greater  than  their  most  excited 
rate  when  the  sense-organs  are  intact  ;  in  other  words,  the  disk  itself 
can  maintain  pulsation  at  a  faster  rate  than  can  the  marginal  sense- 
organs.  The  rate  of  pulsation  in  the  disks  deprived  of  sense-organs 
depends  simply  upon  the  time  required  for  the  waves  to  traverse  the 
circuit  and  restimulate  the  center.  The  wave  travels  faster  through 
peripheral  than  through  the  inner  annuli  of  the  disk.  When  pulsating 
disks  are  suddenly  seized,  moved,  or  otherwise  stimulated,  the  ampli- 
tude of  their  rhythmical  movement  suddenly  increases,  but  the  rate 
remains  practically  the  same,  and  thus  the  presence  of  the  marginal 
sense-organs  is  not  necessary  for  the  display  of  excitement.  The  disks 
of  small  Medusae  pulsate  at  a  faster  rate  than  do  those  of  large  ones, 
other  things  being  equal. 

These  pulsating  disks  may  continue  to  give  regular  rhythmical  con- 
tractions in  sea-  water  for  140  hours  or  more,  but  at  the  end  of  that 
time,  if  they  have  been  deprived  of  their  mouth-arms  and  central 
stomach,  they  become  exhausted,  and  the  amplitude  of  their  pulsa- 
tion decreases,  although  the  rate  remains  practically  constant.  Sud- 
denly the  center  fails  to  restimulate  the  returning  wave,  all  movement 
ceases,  and  the  disk  can  not  be  re-stimulated  until  after  a  period  of 
rest.  Indeed,  the  tissue  appears  much  exhausted  and  responds  feebly 
even  to  the  strongest  stimuli,  such  as  K2SO4,  KC1,  etc.  Complete 
recovery  takes  place,  however,  in  normal  sea-water,  so  that  disks  may 
be  maintained  in  condition  to  pulsate  for  weeks. 

While  in  sea-  water  it  is  almost  impossible  to  set  a  Medusa,  with  mar- 
ginal sense-organs  intact,  into  any  form  of  pulsation  other  than  that 
controlled  by  the  sense-organs.  If,  however,  we  cut  partial  rings  in 
the  sub-umbrella  of  a  Cassiopea,  leaving  the  sense-organs  and  margin 
intact,  and  then  place  the  Medusa  in  a  solution  resembling  sea-water 
but  lacking  calcium,*  all  pulsations  will  cease  in  from  2  to  6  minutes. 
Then,  after  the  Medusa  has  remained  motionless  in  the  solution  for 
one  hour,  if  we  touch  the  disk  for  an  instant  with  a  crystal  of  K2SO4 
it  immediately  springs  into  a  rapid  rhythmical  pulsation  at  a  much 
faster  rate  than  that  previously  maintained  by  the  sense-organs.  This 
pulsation,  indeed,  exhibits  all  of  the  features  shown  by  disks  with- 
out sense-organs,  and  therefore  we  see  that  the  absence  of  calcium  has 


*965  H2O  +  26.74  NaCl  -f  3.75  MgCl2  +  1.64  MgSO*  +  0.85  K2SO4  +  0.07  MgBr, 
or  Van  't  Hoff's  solution  consisting  of  100  NaCl  +  2.2  KC1  +  7.8  MgClg  +  3.8 
MgSOi,  all  of  >6n  concentration. 


34  PULSATION  OF  JELLYFISHES. 

caused  a  paralysis  of  the  marginal  sense-organs ,  but  not  of  the  sub- 
umbrella  tissue  of  the  disk. 

This  we  can  prove  directly,  for  disks  without  sense-organs,  once 
they  be  set  into  pulsation,  will  continue  to  pulsate  for  over  three  hours 
in  a  solution  resembling  sea- water  but  lacking  calcium .  The  amplitude 
of  their  pulsations,  however,  decreases  steadily,  but  may  be  restored 
by  adding  calcium  to  the  solution.  It  is  evident  that  the  central  parts 
of  the  sub-umbrella  of  Cassiopea  may  pulsate  both  in  normal  sea- water, 
and  for  a  long  time  in  sea- water  deprived  of  calcium,  whereas  the  mar- 
ginal sense-organs  are  quickly  paralyzed  by  a  deficiency  of  calcium 
in  the  sea- water.  On  the  other  hand,  perfect  Medusae  and  disks 
deprived  of  sense-organs  will  pulsate  in  sea- water  at  82°  F.  containing 
CaSO4  +  CaCO3  to  saturation,  the  only  effect  being  a  slight  slowing 
of  the  rate  of  pulsation  in  the  case  of  the  perfect  Medusae.  Hence  the 
marginal  sense-organs  require  calcium*  to  perform  their  function, 
whereas  the  general  tissue  of  the  sub-umbrella  is  relatively  unaffected 
by  the  presence  or  absence  of  calcium.  This  is,  however,  a  relative 
matter,  for  while  the  lack  of  calcium  produces  less  effect  upon  the  disk 
than  upon  the  sense-organs,  nevertheless  the  disk  itself  will  finally 
cease  to  pulsate  in  the  absence  of  calcium.  It  is  interesting  to  observe 
that  while  the  disk  is  almost  unaffected  by  a  wide  range  in  the  amount 
of  calcium  in  the  sea- water,  it  is  very  quickly  affected  by  a  change  in 
the  amount  of  the  potassium.  Such  disks  cease  to  pulsate  in  a  few 
minutes  either  in  a  solution  resembling  sea-water  but  lacking  potassium 
or  in  a  solution  of  %  gram  K2SO4  in  100  c.c.  of  natural  sea-water. 
Indeed,  the  center  of  the  disk  is  fully  as  sensitive  to  changes  in  the 
amount  of  potassium  in  the  water  as  is  the  entire  Medusa. 

Under  normal  conditions  pulsation  is  controlled  by  the  marginal 
sense-organs,  the  rate  being  that  of  the  fastest  working  sense-organ. 
The  general  sub-umbrella  surface  has  considerable  influence  in  sus- 
taining the  sense-organs,  for  if  we  reduce  the  area  of  the  sub-umbrella 
enervated  by  the  sense-organs  the  rate  declines.  Normally  the  pul- 
sation is  controlled  by  the  sense-organs,  not  by  centers  of  pulsation  in 
the  undifferentiated  sub-umbrella  tissue.  Among  thousands  of  nor- 
mal Medusae  I  observed  only  two  individuals  in  which  a  center  in  the 
sub-umbrella  controlled  the  pulsation.  These  two  were  pulsating 
slowly  when  I  lifted  them  out  of  water  and  threw  them  forcibly  back. 
They  instantly  began  to  pulsate  in  the  rapid,  uniform,  clockwork-like 
manner  characteristic  of  pulsation  maintained  by  a  center  in  the  sub- 
umbrella,  their  rates  being  fully  four  times  as  great  as  the  normal.  I 
then  cut  off  their  marginal  sense-organs,  and  the  disks  still  continued 

*The  chief  role  of  calcium  is  to  counteract  the  anesthetic  effects  of  magnesium. 


SENSE-ORGANS  AND   PUPATION.  35 

to  pulsate  without  alteration  in  their  rates.  They  both  ceased  in- 
stantly as  soon  as  a  radial  cut  was  completed  from  center  to  margin, 
thus  breaking  the  circuit  of  the  waves  of  contraction. 

We  have  seen  that  a  center  of  pulsation  in  the  undifferentiated  sub- 
umbrella  tissue  sends  out  its  stimulus  only  when  the  contraction  wave 
returns  to  it  through  the  circuit,  and  that  therefore  the  rate  must  be 
constant,  for  it  depends  only  upon  the  length  of  the  circuit  and  the 
rapidity  of  the  wave  ;  and  no  pulsation  can  be  maintained  by  a  center 
in  the  sub-umbrella  tissue  unless  the  contraction  wave  can  pass  through 
a  circuit  and  finally  travel  back  to  restimulate  the  center. 

The  marginal  sense-organs  behave  differently.  They  send  forth  the 
stimulus,  which  produces  contraction,  at  a  slow,  irregular  rate,  and 
they  are  not  restimulated  into  immediate  action  by  a  returning  wave, 
and  can  maintain  tissue  in  pulsation  even  if  its  shape  is  not  that  of  a 
closed  circuit.  They  function  only  when  calcium  is  present  in  solu- 
tion in  the  sea-water,  and  if  lifted  out  of  water  and  dried  with  blotting 
paper  they  cease  in  a  few  minutes  to  initiate  pulsations  ;  but  if  then 
they  be  moistened  with  distilled  water  containing  the  amount  of  cal- 
cium found  in  sea-water,  they  recommence  pulsation.  Indeed,  the 
sense-organs  behave  as  if  a  slow  chemical  change  takes  place  within 
them,  the  result  being  a  contraction-stimulus;  and  this  state  of  con- 
traction in  turn  reducing  the  built-up  compounds  to  their  original 
condition.  Calcium  has  the  peculiar  power  to  offset  the  stupefying 
influence  of  the  magnesium  of  the  sea- water,  but  calcium  is  of  primary 
importance  only  when  magnesium  is  present.  If  magnesium  be  absent 
the  presence  of  calcium  is  relatively  unimportant  in  the  pulsation  of 
Cassiope.a.  Indeed,  the  Medusa  pulsates  longer  and  faster  in  a  solution 
containing  the  amounts  and  proportions  of  NaCl  +  KCL,  found  in  sea- 
water  than  it  does  in  NaCl  +  CaCl2. 

Before  closing  the  account  of  these  experiments  upon  disks  it  should 
be  stated  that  the  disks  of  Aurelia  flavidula  and  Dactylometra  quin- 
quecirra  may  also  be  set  into  sustained  and  regular  rhythm  by  cutting 
partial  rings,  as  has  been  described  in  the  case  of  Cassiopea.  These 
Scyphomedusse,  however,  soon  recover  to  some  extent  from  the  loss 
of  their  marginal  sense-organs,  and  the  chief  difference  between  their 
usual  behavior  after  the  loss  of  the  margin  and  their  behavior  when 
cut  by  partial  rings  and  then  set  into  pulsation  is  that  in  the  latter 
case  the  pulsation  is  of  machine-like  regularity  and  without  pauses, 
whereas  under  normal  conditions  it  is  irregular.  Dactylometra  is  more 
favorable  for  these  experiments  than  Aurelia,  for  Aurelia  is  extremely 
sensitive  to  mechanical  shocks  and  to  chemical  stimuli.  It  is  of 
interest  to  observe  that  the  rate  at  which  the  tissues  of  the  disk  of 


36  PULSATION   OF  JELLYFISHES. 

Dactylometra  maintain  these  pulsations  is  only  a  little  higher  than  that 
maintained  by  its  marginal  sense-organs.  For  example,  a  Dactylo- 
metra which  pulsated  39  times  per  minute  when  intact  pulsated  46 
times  per  minute  with  perfect  regularity  when  all  sense-organs  were 
removed  and  partial  rings  were  cut  in  its  sub-umbrella. 

It  will  be  recalled  that  Romanes  briefly  mentions  a  specimen  of  the 
hydromedusa  Staurophora  ladniata,  in  which  there  were  three  centers 
of  spontaneous  contractions  after  the  bell  margin  was  removed.  I  have 
not  succeeded  in  causing  the  disk  of  Gonionemus  to  pulsate  contin- 
uously by  cutting  partial  rings  in  its  sub-umbrella  after  the  margin 
had  been  removed.  There  were,  however,  but  a  few  small  specimens 
at  my  disposal.  As  Yerkes  found,  the  central  disk  of  Gonionemus , 
when  deprived  of  its  margin,  often  gives  isolated  contractions  without 
external  stimulation. 

III.    REACTIONS  OF  CASSIOPEA  TO  CHEMICAL  STIMULI. 
CHEMICAL   STIMULATION   OF   PARALYZED   DISKS. 

As  we  have  seen,  the  loss  of  the  marginal  sense-organs  paralyzes 
the  disk  of  Cassiopea,  but  it  still  reacts  strongly  by  contractions  if  the 
surface  of  its  sub -umbrella  be  touched  by  certain  substances,  while 
others  have  no  effect  upon  it. 

Strong  solutions  or  crystals  of  the  following  produce  contractions: 
KA1(S04)2,  KBr,  KCN,  K2CO3,  KC1,  KC1O3,  K2CrO4,  K2Cr2O7, 
K8Fe2C12N126H20,  KI,  KMnO4,  KNO3,  KOH,  KHSO4,  K2SO4, 
K2S2O7;  also  Na2CO3,  NaHCO3,  NaCl,  NaClO3,  Na2HPO412H2O, 
NaNO3,  NaOH,  NaSO37H2O,  Na-jSO^OHgO,  and  sodium  oxalate  ; 
also  I,iCl,  BaCl22H2O,  BaSO4,  Ba(OH)2,  NH4OH,  glycerin,  dextrose, 
CuSO4,  Fe2Cl6,  PtCl2,  and  iodine,  etc.  Contractions  are  also  produced 
by  very  weak  solutions  of  the  following  acids :  Acetic,  chromic,  oxalic, 
sulphuric,  hydrochloric,  picric,  nitric,  and  formic.  This  effect  is  doubt- 
less due  to  hydrogen,  the  only  element  common  to  all  of  these  acids. 

The  following  substances  produce  no  contractions,  even  when  the 
crystals  themselves,  or  their  saturated  solutions,  are  applied  to  the 
surface  of  the  sub -umbrella  :  MgBr,  MgCl2,  MgCO3,  MgSO4;  also 
CaCO3,  CaCl2,  CaO,  CaSO4,  and  SrCO3,  SrCl26H2O,  SrSO4,  HgCl2, 
FeS047H20,  CH4N2O. 

Summarizing  the  above,  we  see  that  all  salts  of  potassium,  sodium, 
lithium,  barium,  and  platinum  produce  contractions,  as  do  also  weak 
solutions  of  acids,  glycerin,  dextrose,  ammonia,  and  iodine.  By  far 
the  strongest  contractions  are  produced  by  potassium  salts,  while 
sodium  salts  produce  much  weaker  effects.  Nevertheless  the  NaCl 
of  sea-water  is  a  more  powerful  stimulant  than  the  potassium  (K2SO4 


REACTION  TO   CHEMICALS.  37 

or  KC1),  owing  to  its  far  greater  amount.  The  salts  of  calcium,  mag- 
nesium, and  strontium  do  not  stimulate  the  disk  and  fail  to  produce 
contractions,  even  when  in  saturated  solutions. 

Combinations  of  Mg  or  Ca  with  Na  or  K  may  or  may  not  give  con- 
tractions, for  the  Mg  always,  and  Ca  in  some  cases,*  tends  to  inhibit 
pulsation.  Thus  a  series  of  contractions  are  produced  by  5K2So4.- 
Na2SO4,  Na2S04.3K2S04,  MgCl2.2KC1.6H2O,  K2Mg(SO4)2,  Na2Mg- 
(SO4)24H2O,  K2Ca(SO4)22H2O.MgSO4,  MgCl2K2SO46H2O,  and  Mg- 
Cl2.NaC1.2H2O;  the  first  named  giving  powerful  and  the  last  weak 
contractions.  On  the  other  hand,  Ca2K2Mg(SO4)2  and  CaCl2.2MgCl2.- 
12H2O  give  no  contractions.  The  salts  act  in  accordance  with  their 
mass-effects.  It  is  interesting  that  solutions  of  the  ashes  of  the 
Medusa  will  not  produce  contractions,  although  Merunowicz  (1875) 
found  that  an  aqueous  solution  of  the  ashes  of  the  blood  will  stimu- 
late the  vertebrate  heart  into  action. 

Loeb  (1905)  states  that  Ba,  Li,  Na,  Rb,  Cs,  F,  Cl,  Br,  and  I  are  capa- 
ble of  bringing  about  contractions  in  skeletal  muscles ;  whereas  K, 
Mg,  Ca,  Sr,  Mn,  and  Co  give  rise  to  no  contractions  or  inhibit  them. 

It  is  evident  that  the  stimulating  effects  of  the  electrolytes  are  gen- 
erally due  to  their  cations  rather  than  to  their  anions,  but  contrac- 
tions may  also  be  produced  by  substances  which  can  not  be  ionized, 
such  as  glycerin  and  dextrose,  and  weak  contractions  are  sometimes 
produced  by  CaBr2,  the  effect  being  due  to  the  bromine.  It  will  be 
recalled  that  Greene  (1899)  and  Ho  well  (1901)  also  found  that  heart 
muscle  will  pulsate  in  pure  solutions  of  cane  sugar  and  dextrose, 
and  I  find  that  the  heart  of  Salpa  and  the  branchial  arms  of  Lepas 
will  also  pulsate  in  dextrose  or  glycerin.  In  his  former  papers  L,oeb 
maintained  that  rhythmic  pulsation  was  impossible  in  non-ionizable 
solutions,  but  his  views  appear  to  have  changed  upon  this  point. 

EFFECTS   OF   CALCIUM   IN    RESTORING   PULSATION. 

We  have  the  well-known  experiment  of  Howell  (1898)  and  others 
showing  that  when  heart  muscle  has  ceased  to  beat  in  Ringer's  solu- 
tion it  may  be  made  to  beat  again  for  a  short  time  by  adding  any  cal- 
cium salt.  This  is  also  true  for  Cassiopea,  for  the  Medusa  will  pulsate 
for  a  short  time  in  any  solution  containing  Na  and  K  in  amounts  found 
in  sea-water,  and  then  after  all  pulsations  have  ceased  they  can  be 
revived  by  adding  calcium.  This  is  illustrated  in  the  following  list  of 
trials  (table  3),  wherein  if  the  sodium  chloride  was  replaced  by  any 

*  Taken  alone  calcium  inhibits  or  fails  to  stimulate  pulsation,  but  in  combination 
with  sodium  chloride  and  potassium,  as  in  NaCl  +  KC1  +  CaCl2,  it  becomes  a  power- 
ful stimulant. 


38  PUIvSATlON  OF 

other  salt  this  was  made  isotonic  with  the  NaCl  of  sea-water.  The 
potassium  was  so  introduced  as  always  to  give  the  same  amount  of  the 
element  (K)  as  is  found  in  sea- water. 

TABLE  3. — How  calcium  revives  rhythmical  pulsation  in  Cassiopea  after  all 
movement  has  ceased  in  solutions  contaiuing  Na  or  Li,  isotonic  -with  the  NaCl 
of  sea-zuater,  and  potassium  in  the  same  amount  as  is  found  in  sea-zvater. 


Normal  M  e  d  u  s  ae 
taken  from  sea- 
water  and  placed 
in— 


They  ceased  to  pulsate  in — 


Were  restored  to  pulsation  by 
the  addition  of  any  of  the 
following  calcium  salts,  tried 
separately. 


NaCl  +  KC1 . . . 
NaCl  +  K2S04. 


NaCl  +  KClO3 

Na2C03+K2C03... 


I4O+KC1. 


About  120  minutes 

20  to  30  minutes.    Very  rapid  pulsation 

at  first,  followed  by  periods  of  rest  and 

activity. 
12  to  18  minutes.    Pulsation  not  so  rapid 

as  in  NaCl  +  K2SO4 
4   to    10   minutes.     Pulsation  not  very 

rapid  at  first.    Slower  than  in  NaCl  + 

K2C03 
3  to  7  minutes.     Pulsation    slow    and 

weak. 
Less  than  i  minute.    Pulsation  rapid  at 

first. 

i  to  6  minutes.    Pulsated  slowly  at  first. 


CaCl2,  CaSO4. 

CaS04)  CaCO3,  CaCl2,or  CaH2O2. 


Very   active  pulsation  restor- 
ed by  CaSO4,CaCl2,orCaH2O2. 
CaSO4)  CaCls,  or  CaH2O2. 


CaCO3  revived  weakly. 

CaCla  or  CaH2O2.  Some  of  the 
Medusae  did  not  revive  pul- 
sation. 

CaCl2.  All  three  Medusae 
revived  weakly. 


Table  3  shows  that  Cassiopea  pulsates  longer  and  more  rapidly  in 
a  solution  of  NaCl  +  KC1  than  in  any  other  solution  named  in  the 
above  table.  Also,  sodium  and  potassium  nitrates  are  more  injurious 
than  a  solution  in  which  the  sodium  is  replaced  by  an  isotonic  amount 
of  lithium.  Evidently  the  anions  as  well  as  the  cations  of  the  salts 
have  a  decided  influence  upon  the  rhythmical  movement.  This  is 
also  shown  by  the  fact  that  Medusae  pulsate  longer  and  with  greater 
regularity  of  movement  in  NaCl  +  K2SO4  +  CaSO4  +  CaCO3  than 
they  do  if  we  omit  the  CaCO3  and  replace  it  by  an  equivalent  amount 
of  CaSO4.  It  will  be  recalled  that  Rogers  (1905,  p.  249)  found  that 
the  addition  of  small  amounts  of  Na2CO3  or  NaOH  to  solutions 
have  a  beneficial  effect  in  maintaining  the  rhythm  of  the  crab's  heart, 
and  he  attributes  this  effect  to  the  neutralization  of  small  amounts 
of  free  acid  in  the  solutions.  Ammonia,  KOH,  or  NaOH  in  small 
amounts  have,  however,  little  effect  upon  the  rhythm  of  Cassiopea, 
but  if  the  sea- water  be  rendered  almost  neutral  by  HC1  (it  is  nor- 
mally decidedly  alkaline  at  Tortugas)  the  pulsations  of  the  Medusae 
lose  energy,  and  finally  the  rate  declines,  and  movements,  although 
regular,  are  feeble  and  slow.  Thus  the  rates  of  three  Medusae  declined 
in  six  hours  from  37-50  to  13-17  per  minute,  due  to  the  effect  of  a 
minute  quantity  of  HC1  in  the  sea-water,  causing  it  to  become  almost 
neutral,  but  still  alkaline  to  litmus  test.  It  seems  improbable,  how- 


EFFECTS  OF  SODIUM   AND   CALCIUM.  39 

ever,  that  the  addition  of  CaCO3,  which  improves  the  regularity  of 
pulsation  of  Medusae  in  NaCl  +  K2SO4,  has  only  the  effect  of  neutral- 
izing acids.  Distilled  water  and  the  purest  obtainable  salts  were  used 
in  making  solutions  and  there  is  no  reason  to  suppose  that  there  were 
any  more  free  acids  in  the  solutions  than  in  the  natural  sea-water  itself. 

Physiologists  have  generally  assumed  (see  Howell,  Text-Book  of 
Physiology,  p  502)  that  the  chief  r6le  of  sodium  chloride  in  pulsa- 
tion is  to  maintain  the  osmotic  pressure  of  the  solution.  I  find,  how- 
ever, that  Cassiopea  pulsates  more  than  24  minutes  in  a  solution  of 
Na2SO4  containing  the  same  amount  and  proportion  of  Na  as  is  found 
in  sea- water  ;  whereas  it  will  not  pulsate  more  than  14  minutes  in  a 
solution  of  Na2SO4  isotonic  with  sea-water.  This  would  lead  one  to 
believe  that  the  sodium  of  the  sea-water  exerts  a  specific  action,  and 
that  the  salts  have  a  specific  chemical  effect  independent  of  their 
osmotic  action.  Indeed,  the  various  salts  of  sodium  behave  very 
differently  ;  for  example,  Cassiopea  pulsates  less  than  i  minute  in 
Na2CO3,  ii  to  12  minutes  in  NaClO3,  and  more  than  half  an  hour  in 
NaCl,  or  NaNO3  isotonic  with  sea- water. 

When  pulsations  have  ceased  in  96  c.c.  H2O  +2.7  grams  NaCl  + 
0.085  gram  K2SO4  they  may  be  revived  temporarily  by  Na2CO3,  more 
NaCl,  KC1,  K2CO3,  or  weak  acids.  These  cause  only  a  few  irregular 
contractions,  however,  and  are  quite  different  in  their  effects  from 
the  long,  steady  revival  of  pulsation  upon  the  addition  of  calcium. 
Potassium  is,  however,  capable  of  reviving  temporary  pulsation  in 
any  solution  which  lacks  magnesium,  but  if  magnesium  be  present  it 
can  not  usually  revive  pulsation.  It  is  interesting  to  observe  that 
after  Medusse  have  ceased  to  pulsate  in  the  NaCl  +  K2SO4  and  have 
been  revived  by  potassium,  they  will  not  again  pulsate  upon  the  addi- 
tion of  calcium  to  the  solution.  On  the  other  hand,  if  pulsations  have 
ceased  and  have  been  revived  by  adding  more  sodium,  they  can  be 
revived  a  second  time  by  adding  calcium.  Potassium  in  excess  at 
first  stimulates  the  disk  powerfully,  but  soon  it  poisons  the  tissues  and 
inhibits  the  sensibility,  while  calcium  is  not  a  stimulant,  but  is  neces- 
sary for  pulsation  in  connection  with  sodium  and  potassium.  The 
chief  r61e  of  calcium  is,  however,  to  counteract  the  inhibiting  effect 
of  the  magnesium. 

This  is  shown  by  the  fact  that  if  we  were  to  place  Cassiopea  in  nor- 
mal sea- water,  and  then  add  sufficient  sodium  oxalate  to  precipitate 
the  calcium,  pulsation  ceases  in  less  than  five  minutes,  but  is  quickly 
restored  if  we  place  the  Medusa  in  NaCl  +  KC1  +  sodium  oxalate,  or 
in  NaCl  +  KC1.  Pulsation  is  not  restored,  however,  if  we  place  the 
Medusa  in  NaCl  +  magnesium.  These  experiments  prove  that  the 


40  PULSATION  OF  JELLYFISHES. 

pulsation  is  inhibited  by  the  magnesium  of  the  sea-water,  not  merely  by 
the  loss  of  calcium ;  for  pulsation  may  be  restored  in  solutions  which 
lack  calcium.  They  also  show  that  when  calcium  is  present  the 
magnesium  does  not  inhibit  pulsation. 

EFFECTS   OF   MAGNESIUM   UPON   PULSATION. 

The  magnesium  salts  in  sea- water  retard  pulsation  in  Cassiopea,  and 
reduce  its  rate,  amplitude,  and  energy.  Cassiopea  pulsates  at  about 
twice  its  normal  rate  in  a  solution  resembling  sea-water  but  lacking 
magnesium,  but  if  we  add  the  magnesium  to  this  solution  the  Medusa 
immediately  pulsates  at  normal  rates.  Also,  an  excess  of  magnesium 
added  to  sea- water  causes  the  rate  and  energy  of  pulsation  to  decline, 
although  Medusae  will  tolerate  1.6  grams  MgCl2  in  100  c.c.  sea-water, 
and  will  pulsate  slowly  for  half  an  hour  without  the  least  apparent 
injury,  their  normal  rate  being  regained  in  a  few  minutes  after  they 
are  returned  to  pure  sea-water.  Magnesium  acts  only  as  a  restrainer, 
never  stimulating  the  disk  of  Cassiopea.  When  the  disk,  deprived  of 
marginal  sense-organs,  is  placed  in  a  solution  of  MgCl2  or  MgSO4 
isotonic  with  sea- water  it  does  not  pulsate.  Indeed,  the  rate  of  pulsa- 
tion of  normal  Medusae  in  natural  sea-water  becomes  successively 
slower  as  we  add  more  and  more  magnesium. 

The  r61e  of  magnesium  is,  however,  an  essential  one  in  pulsation, 
for  it  counteracts  the  strongly  stimulating  action  of  the  combination 
of  NaCl,  K,  and  Ca  which  occurs  in  Ringer's  solutions,  or  in  sea-water. 
For  example,  if  we  place  Cassiopea  in  a  solution  of  NaCl  +  KCl  +  CaCl2 
in  amounts  and  proportions  found  in  sea-water  *  the  Medusa  is  highly 
stimulated  and  pulsates  at  fully  twice  its  normal  rate.  If  now  we  pre- 
cipitate the  magnesium  in  its  tissues  in  any  manner, f  the  stimulating 
effect  of  the  sodium,  potassium,  and  calcium  is  unchecked,  and  after  a 
short  period  of  violent  pulsation  the  Medusa  passes  into  a  strong  sus- 
tained tetanus  and  remains  motionless,  with  its  bell  highly  contracted. 

I  find  also  that  sustained  pulsation  is  impossible  in  the  heart  of 
Salpa  or  the  branchial  arms  of  Lepas  unless  magnesium  be  present, 
and  that  in  these  cases  also  NaCl+KCl  +CaCl2  is  a  powerful  stimu- 
lant, producing  rapid  but  not  permanently  sustained  pulsation,  but 
normal  sustained  pulsation  is  attained  on  the  addition  of  magnesium. 
It  appears,  therefore,  that  a  Ringer's  solution  is  not  an  inorganic  food 
for  the  pulsating  organ,  as  has  been  commonly  assumed  by  physiol- 

*100  NaCl  +  2.2  KC1  +  3  CaCl2  all  of  >£n  concentration,  as  in  Van  't  Hoff's  solu- 
tion. 

f  The  magnesium  maybe  precipitated  by  a  small  amount  of  Ba(OH)2,  KOH,  NaOH, 
or  sodium  phosphate  -}-  ammonia  -f-  ammonium  chloride,  etc. 


ANESTHETIC  EFFECTS  OF  MAGNESIUM.  41 

ogists,  but  is  only  a  stimulant  which  in  the  end  produces  injurious 
effects  by  the  withdrawal  of  magnesium  through  osmosis.  It  can  not 
sustain  permanent  pulsation  unless  a  certain  proportion  of  magnesium 
be  present  to  preserve  a  balance. 

It  is  interesting  to  see  that  Meltzer  and  Auer  (i9O5-'o6)  find  that 
magnesium  affects  the  nervous  system  in  such  manner  as  to  produce 
in  mammals  a  deep  anesthesia,  with  relaxation  of  all  the  voluntary 
muscles.  It  is  inhibitory,  never  stimulating  in  its  effects,  but  it  does 
not  interfere  with  the  trigeminal  reflex  inhibition  of  respiration .  Also, 
Carlson  (1906)  finds  that  magnesium  and  calcium  depress  the  gan- 
glionic  rhythm  of  the  heart  of  Limulus  without  primary  stimulation. 
Indeed,  the  anesthetic  effects  of  magnesium  salts  upon  aquatic  animals 
have  been  known  since  Tullberg's  researches  in  1892. 

Macallum  (1903)  finds  that  there  is  about  10  per  cent  less  magnesium 
in  the  bodies  of  Cyanea  and  Aurelia  than  in  sea- water.  Rogers  (1905), 
however,  found  that  the  optimum  solution  for  the  continuance  of 
rhythmic  movement  of  the  crab's  heart  contains  fully  as  much  magne- 
sium as  the  sea-water. 

I,oeb  (1906)  finds  that  in  Polyorchis  the  NaCl  +  KC1  +  CaCl2  of  sea- 
water  produce  sustained  contraction  without  pulsation,  and  that 
magnesium  is  necessary  in  order  to  overcome  the  tetanus  and  permit 
of  rhythmical  pulsation.  Also,  this  effect  of  magnesium  can  be  inhib- 
ited by  the  addition  of  an  equivalent  amount  of  calcium  or  potassium. 
Also,  Romanes  (1885)  found  that  the  vigor  of  the  swimming  move- 
ments of  Sarsia  is  impaired  in  a  pure  NaCl  solution  of  the  same 
strength  as  that  of  the  sodium  chloride  in  sea- water,  but  that  this  vigor 
of  movement  is  somewhat  restored  by  adding  MgSO4  to  the  same  amount 
found  in  sea- water.  In  the  case  of  Cassiopea  all  movement  would 
cease  in  less  than  six  minutes  in  NaCl  +  MgSO4  in  amounts  found  in 
sea-water ;  whereas  irregular  pulsation  continues  for  half  an  hour  in 
NaCl  alone,  although  after  that  the  Medusae  would  show  periods  of 
quiescence  alternating  with  periods  of  pulsation.  I  find  also  that 
i  per  cent  magnesium  added  to  sea-water  slowly  lowers  the  rate  of 
the  rhythmical  movement  of  the  arms  of  Lepas.  It  seems  probable, 
therefore,  that  magnesium,  while  always  inhibitory,  plays  a  somewhat 
different  role  in  the  efficiency  of  its  control  over  rhythmical  movement 
in  various  animals. 

EFFECTS   OF  POTASSIUM   UPON  PULSATION. 

Potassium  in  small  amounts  temporarily  stimulates  and  then  retards 
pulsation.  Unlike  magnesium  or  calcium  in  excess,  it  is  quite  poi- 
sonous. All  potassium  salts,  with  the  exception  of  those  consisting 


42  PULSATION  OK 

of  combinations  of  potassium  with  magnesium  and  calcium,  are  pow- 
erful stimulants  to  the  disk  of  Cassiopea,  causing  strong  but  temporary 
contractions.  Repeated  touches  of  a  crystal  of  K2SO4  to  any  one  spot 
on  the  sub -umbrella  of  Cassiopea  soon  renders  the  place  insensitive  to 
further  stimulation  of  any  sort.  For  example,  a  single  spot  upon  a 
disk,  deprived  of  sense-organs,  was  touched  17  times,  in  rapid  succes- 
sion, with  a  crystal  of  K2SO4  and  each  time  a  contraction  resulted. 
The  next  2  touches,  however,  gave  no  contractions;  then  followed  2 
touches  with  contractions,  7  without  contractions,  i  with,  and  finally 
ii  without  contractions,  etc. 

If  normal  Cassiopea  with  sense-organs  intact  be  placed  in  sea-water 
+  0.125  to  1.55  per  cent  K2SO4,  KC1O3,  KC1,  or  K2CO3  they  immedi- 
ately pulsate  at  an  abnormally  high  rate,  but  the  movement  soon 
loses  force,  and  the  disk  comes  to  rest  expanded  with  the  mouth-arms 
strongly  contracted.  Medusae  in  0.125  Per  cent  excess  of  K2SO4  will 
pulsate  quickly  at  first  and  then  more  and  more  slowly,  so  that  at 
the  end  of  1 3  hours  their  rates  are  only  about  half  the  normal  rate  in 
sea-water.  On  the  other  hand,  Medusae  in  sea-water  +  1.55  per  cent 
K2SO4  will  pulsate  with  great  activity  for  a  few  moments,  but  will 
cease  all  movement  in  less  than  4  minutes.  Also,  a  solution  of  K2SO4 
isotonic  with  the  NaCl  of  sea-water  at  once  reduces  the  rate  of  pulsa- 
tion of  normal  Medusae  and  quickly  brings  them  to  rest  without  an 
initial  display  of  excitement.  It  appears  that  a  small  excess  of  potas- 
sium acts  as  a  temporary  stimulus,  whereas  a  large  excess  at  once 
inhibits  pulsation.  It  is  possible  that  the  initial  stimulation  is  due 
to  the  physiological  reaction  of  the  tissues  against  the  injurious 
effects  of  the  potassium.  Temporary  activity  is  commonly  called 
forth  in  animals  by  sudden  injurious  stimuli.  In  this  connection  it 
is  interesting  to  see  that  Carlson  (1906)  finds  that  potassium  is  a 
primary  stimulant  for  the  heart  of  Limulus,  but  its  action  is  quickly 
followed  by  depression. 

An  excess  of  i  per  cent  potassium  in  the  sea-water  quickly  lowers 
the  rate  of  movement  of  the  arms  of  Lepas,  causes  tetanus-like  con- 
traction, and  may  be  fatal  in  10  minutes. 

The  effect  of  potassium  upon  the  disk  without  marginal  sense- 
organs  is,  however,  different  from  its  effect  upon  the  normal,  perfect 
Cassiopea ,  for  disks  without  sense-organs  are  actively  stimulated  into 
pulsation  for  a  short  time  in  all  excess  of  potassium  from  sea-water  + 
0.25  per  cent  K2SO4  to  a  pure  solution  of  K2SO4,  or  KC1,  isotonic 
with  the  NaCl  of  sea -water.  Perfect  Medusae,  however,  show  no 
increase  in  rate  of  pulsation  in  isotonic  K2SO4,  but  steadily  decline. 
It  seems  probable,  therefore,  that  a  strong  excess  of  potassium  impairs 


EFFECTS  OF  POTASSIUM.  43 

the  activity  of  the  marginal  sense-organs  sooner  than  it  affects  the 
disk  itself.  The  disk  without  sense-organs  will,  however,  cease  to  pul- 
sate in  a  solution  resembling  sea -water  but  lacking  potassium  quite 
as  quickly  as  will  the  perfect  Medusa.  It  would  seem,  therefore,  that 
the  sense-organs  and  the  sensory  surface  of  the  sub-umbrella  are 
equally  intolerant  of  a  lack  of  potassium  in  the  sea- water.  This  is 
interesting  in  view  of  the  fact  that  the  disk  without  sense-organs  is 
relatively  indifferent  to  calcium,  or  magnesium,  and  will  pulsate  either 
in  sea- water  saturated  with  CaSO4,  in  normal  sea- water,  or  for  more 
than  an  hour  in  a  solution  resembling  sea- water  but  without  calcium. 
The  Medusa  with  sense-organs  intact,  however,  ceases  to  pulsate  in 
a  solution  containing  all  of  the  elements  of  sea-water  excepting  cal- 
cium in  less  than  six  minutes,  but  will  pulsate  in  sea- water  satu- 
rated with  CaSO4.  It  is  evident  that  the  accurate  balance  between  the 
proportions  of  calcium,  potassium,  and  sodium  insisted  upon  by  L,oeb 
as  being  necessary  for  the  continuance  of  pulsation  need  not  be  main- 
tained and  yet  pulsation  may  continue.  As  Howell  has  pointed  out, 
marine  animals  are  attuned  to  the  sea- water  in  which  they  live,  and 
any  change  in  its  constituents  must  be  expected  to  affect  them  more 
or  less  adversely.  Loeb's  theory  of  the  influence  of  ions  upon  pulsa- 
tion, although  of  fundamental  value,  unfortunately  neglects,  in  some 
measure,  to  consider  the  effects  of  the  salts  as  a  whole.  As  we  shall 
soon  see,  however,  Cassiopea  will  pulsate  for  at  least  30  minutes  in  a 
pure  ^n  NaCl  solution,  whereas  it  is  paralyzed  in  less  than  a  minute 
in  an  isotonic  solution  of  Na2CO3.  Indeed,  the  various  potassium 
salts  stimulate  in  different  degrees.  KI,  K2SO4,  and  KC1  are  powerful 
stimulants,  whereas  KMnO4,  KA1(SO4)2,  and  potassium  metabisulphite 
produce  weak  contractions. 

Matthews  (1905)  concludes  that  valence,  as  such,  either  of  the  anion 
or  cation,  is  of  secondary  or  no  importance  in  determining  either  the 
toxic  or  antitoxic  action  of  the  salt. 

L,oeb  (1900)  concluded  that  the  potassium  and  calcium  ions  of  sea- 
water  prevent  the  center  of  the  bell  of  Gonionemus  from  pulsating 
rhythmically.  His  experiment,  however,  does  not  prove  this  point, 
for  he  found  that  the  center  of  the  bell  of  Gonionemus  would  pulsate 
in  ^n  NaCl,  but  not  in  sea- water ;  and  thus  he  concluded  that  the  K 
and  Ca  of  sea-water  inhibited  pulsation,*  but  he  neglected  to  consider 

*While  this  paper  was  in  press  Loeb  (1906  :  Journ.  Biol.  Chemistry,  vol.  i,  p.  431) 
concludes  that  magnesium  and  calcium  inhibit  the  center  of  Gonionemus.  In  so  far 
as  the  effect  of  magnesium  is  concerned  his  view  now  accords  with  the  researches  of 
Tullberg  (1892),  Meltzer  and  Auer  (1905-06),  and  Mayer  (1906)  that  magnesium  is 
anesthetic  or  inhibitory. 


44  PULSATION  OF  JEUvYFlSHES. 

the  effects  of  magnesium.  I  find,  indeed,  that  the  center  of  the  bell 
of  Gonionemus  does  occasionally  pulsate  spontaneously  in  sea-water, 
and  always  pulsates  actively  whenever  one  touches  it  with  a  crystal  of 
KC1  or  K2SO4.  It  is  not  stimulated  by  the  sea-water,  but  the  inhib- 
itory effect  of  the  sea- water  is  probably  due  to  magnesium,  not  to 
potassium  or  calcium.  The  center  of  Gonionemus  is  strongly  stimu- 
lated by  Na  salts,  and  the  reason  it  pulsates  in  ^n  NaCl  is  that  magne- 
sium ,  as  well  as  calcium  and  potassium,  is  withdrawn  from  the  tissues 
by  osmosis  by  the  pure  NaCl  solution,  thus  giving  a  preponderating 
influence  to  the  Na,  which  acts  as  a  stimulant.  Indeed,  L,oeb  himself 
found  that  the  center  of  Gonionemus  pulsates  slowly  in  96  c.c.  ^n  NaCl 
+  2  c.c.  ^n  KC1  +  2  c.c.  10/8n  CaCl2.  I  also  find  that  Gonionemus 
pulsates  slowly  but  without  pauses  in  a  solution  resembling  sea-water* 
but  lacking  magnesium  salts.  The  characteristic  pauses  which  occur 
periodically  in  the  normal  pulsation  of  Gonionemus  are  thus  due  to 
magnesium.  Magnesium  fails  to  stimulate  the  center  of  Gonione- 
mus, and,  indeed,  if  the  center  be  touched  with  MgSO4  or  MgCl2  it 
deadens  the  part  touched,  so  that  it  responds  weakly  or  not  at  all  to 
such  powerful  stimuli  as  the  touch  of  a  crystal  of  NaCl  or  K2SO4. 
The  disk  of  Cassiopea  deprived  of  sense-organs  behaves  exactly  as  does 
Gonionemus,  for  it  does  not  pulsate  spontaneously  in  sea- water  but 
does  so  in  ^n  NaCl,  or  in  any  solution  containing  NaCl  +  K  or  Ca, 
but  lacking  magnesium.  If,  however,  we  stimulate  it  with  KC1  or 
K2SO4  it  gives  some  active  pulsations  in  sea- water  ;  or  better  still,  if 
we  cut  partial  rings  in  its  sub-umbrella  and  then  stimulate  it  mechan- 
ically by  a  shock,  it  pulsates  indefinitely  in  sea- water. 

It  is  significant  that  the  disks  of  Aurelia  and  Dactylometra,  when 
deprived  of  marginal  sense-organs,  still  pulsate  irregularly  in  sea- 
water;  and  the  disks  of  both  of  these  Scyphomedusae  sometimes 
respond  by  weak  contractions  to  MgSO4  and  MgCl2.f  They  therefore 
pulsate  in  sea-water  as  soon  as  they  recover  from  the  shock-effects 
resulting  from  loss  of  their  marginal  sense-organs,  because  their 
disks  are  stimulated  by  everything  (Na,  K,  Mg)  in  the  sea -water, 
except  the  calcium,  which,  taken  singly,  exerts  only  a  slight  inhibitory 
action.  In  the  case  of  Cassiopea,  Gonionemus,  and  Poly  orchis  the  sea- 
water  is  a  balanced  fluid.  •  Na  stimulates  while  Mg  inhibits  pulsation. 
Ca  in  connection  with  Na  and  K  is  necessary  to,  and  stimulates, 
pulsation . 

*  96  c.c.  H8O  4-  2.7  grams  NaCl  +  0.124  CaSO4  +  0.01  CaCO3  +  0.085  K2SOi. 

f  These  reactions  are  so  irregular  and  the  Medusae  so  extremely  sensitive  to  mechan- 
ical effects  that  I  am  in  doubt  concerning  the  validity  of  this  statement.  It  may  be 
that  the  occasional  response  is  due  to  some  chemical  shock-effect. 


EFFECTS  OF  CALCIUM. 


45 


The  disk  of  Cassiopea  does  not  pulsate  in  sea- water,  because  the 
sea- water  as  a  whole  does  not  stimulate  it.  Disks  of  Aurelia  and 
Dactylometra  behave  in  sea-water  as  if  they  were  weakly  stimulated. 

Howell  (1901,  pp.  200,  204)  concludes  as  a  result  of  his  own  work 
and  a  review  of  the  labors  of  others  that  potassium  acts  somewhat  as 
an  inhibitory  agent  upon  the  rhythmical  pulsation  of  the  heart  muscle 
of  the  ventricle  of  the  terrapin,  for  it  lengthens  the  period  of  diastole, 
causing  the  rate  to  become  slower,*  but  at  the  same  time  the  heart 
muscle  pulsates  longer  when  potassium  is  present  than  it  does  when 
only  sodium  and  calcium  are  present.  A  small  excess  of  potassium  in 
physiological  doses  is  not  toxic  in  its  effects,  yet  it  inhibits  the  pulsa- 
tion of  the  heart  muscle;  but  the  muscle  will  beat  again  in  solutions 
containing  less  potassium  or  more  calcium.  Other  physiologists  con- 
clude that  small  amounts  of  potassium  stimulate  "the  vertebrate 
heart."  (See  Carlson,  1906,  p.  397.) 

It  is  interesting  to  observe  that  Macallum  (1903)  finds  that  the 
bodies  of  Cyanea  and  Aurelia  contain  considerably  more  potassium 
than  does  sea- water.  He  found  the  various  elements  to  exist  in  the 
following  proportions  : 


Na. 

Ca. 

K. 

Mg. 

Sea.-wa.ter  

IOO 

3.84 

3.66 

II.QQ 

Cyanea  arctica  .  .  . 
Aurelia  flavidula.  . 

100 
IOO 

3-86 
4-13 

7.67 
5.i8 

11.31 
11.43 

INFLUENCE  OF  CALCIUM   UPON  PULSATION. 

Calcium  is  essential  for  pulsation  on  account  of  its  power  to  coun- 
teract the  inhibiting  influence  of  magnesium.  Its  importance  in  con- 
nection with  sodium  and  potassium  in  maintaining  pulsation  has  been 
known  since  Ringer's  important  experiments  in  1883. 

If  we  place  perfect  Medusae  of  Cassiopea,  with  marginal  sense- 
organs  intact,  in  a  solution  resembling  sea-water  but  merely  lacking 
calcium,t  the  Medusae  pulsate  more  and  more  weakly,  and  all  move- 
ment ceases  in  less  than  6  minutes.  The  Medusae  are  not  poisoned, 
however,  for  if,  after  remaining  motionless  for  fully  an  hour  we  add 
calcium  to  the  solution,  or  restore  the  Medusae  to  sea-water,  pulsation 
is  resumed  almost  at  once,  beginning  feebly  at  first  but  rapidly  regain- 
ing its  normal  vigor  in  a  few  minutes. 

*I  find  that  in  the  embryo  loggerhead  turtle,  14  days  old,  the  heart  pulsates  faster 
in  NaCl  +  KC1  than  it  does  in  pure  NaCl. 

|96  c.c.  CH20  +  2.7  grams  NaCl +  03.7  gram  MgCl2  +  0.16  gramMgSO*  +  0.085 
gram  K2SOi(  or  100  NaCl  +  2.2  KC1  +  7.8  MgClg  +  3.8  MgSo*,  all  of  f£n  concentra- 
tion. 


46  PUIvSATlON  OF  JELLYFISHES. 

The  Medusae  are,  however,  inhibited  from  pulsating  by  the  presence 
of  magnesium,  not  by  the  mere  absence  of  calcium  ;  for  if  magnesium 
be  absent,  calcium  may  also  be  absent  and  the  Medusae  will  pulsate 
fully  two  hours. 

A  large  excess  of  calcium  lowers  the  rate  of  pulsation  of  Cassiopea  > 
after  a  momentary  increase.  The  inhibitory  effect  of  calcium  is,  how- 
ever, far  less  marked  than  that  of  magnesium,  or  than  the  final  toxic 
effect  of  potassium.  For  example,  if  we  add  CaSO4  +  CaCO3  to  sea- 
water  at  82°  F.,  to  saturation,  normal  perfect  Medusae  of  Cassiopea 
pulsate  at  about  two-thirds  their  normal  rate  after  being  in  this  solu- 
tion 12%  hours.  One  gram  of  CaCl2  in  100  c.c.  sea- water  also  slightly 
reduces  the  rate  of  pulsation  without  injurious  effects,  recovery  being 
almost  immediate  in  normal  sea- water.  Perfect  Cassiopea  with  sense- 
organs  intact  when  placed  in  a  pure  solution  of  CaCl2  isotonic  with 
the  NaCl  of  sea-water  ceases  to  pulsate  in  10  seconds,  and  can  not  be 
restored  to  pulsation  by  being  placed  in  NaCl  +  K2SO4  in  amounts 
found  in  sea-water.  A  strong  solution  of  K3SO4  in  NaCl,  however, 
revives  them  into  active  pulsation.  Evidently  their  sensibility  to 
stimuli  is  impaired  but  not  destroyed. 

Calcium  salts  never  stimulate  the  disk  of  Cassiopea  into  pulsation, 
even  when  placed  upon  it  in  concentrated  solutions. 

We  see  that  calcium,  while  not  of  itself  a  stimulant,  is  necessary  to 
pulsation  and  is  a  stimulant  in  connection  with  sodium  and  potassium. 
An  excess  of  calcium  tends  to  retard  pulsation,  but  even  a  saturated 
solution  of  CaSO4  in  sea- water  exerts  no  appreciable  toxic  influence. 
It  is  far  more  important  to  pulsation  than  potassium  ;  for  Cassiopea 
will  pulsate  for  more  than  an  hour  with  irregular  periods  of  rest  and 
activity  in  the  absence  of  potassium,  but  in  the  absence  of  calcium 
pulsation  ceases  in  less  than  6  minutes.  This  importance  is  due  solely 
to  the  remarkable  ability  which  calcium  has  to  counteract  the  inhibit- 
ing effect  of  magnesium. 

EFFECTS   OF  SODIUM   UPON   PULSATION. 

All  of  the  sodium  salts  are  weak  stimulants  to  the  disk  of  Cassiopea 
deprived  of  its  marginal  sense-organs,  producing  not  very  powerful 
contractions.  The  sodium  salts,  however,  vary  considerably  in  their 
stimulating  power,  NaCl  or  NaOH  giving  strong  and  Na2CO3  or 
Na2SO4  weak  contractions. 

The  disk  of  Cassiopea  deprived  of  marginal  sense-organs  pulsates 
for  about  20  minutes  in  a  pure  £/6n  NaCl  solution,  and  also  in  NaCl  + 
K2SO4  or  NaCl+K2SO4+CaSO4  or  NaCl+CaSO4.* 

*  The  proportions  of  Na,  Ca,  and  K  were  such  as  are  found  in  sea-water. 


EFFECTS  OF  SODIUM. 


47 


It  will  not  pulsate,  however,  in  NaCl+  MgSO4  or  MgCl2  or  both, 
and  it  is  evident  that  the  magnesium  salts  contained  in  sea-water 
counteract  the  stimulating  effect  of  the  sodium.  Disks  that  have 
ceased  to  pulsate  in  ^n  NaCl  will  revive  a  few  pulsations  if  supplied 
with  calcium,  or  with  a  strong  excess  of  potassium,  or  both,  but  no 
revival  results  when  magnesium  is  added  to  the  NaCl  solution. 
Indeed,  it  may  be  said  of  the  sea- water  that  the  chief  stimulant, 
owing  to  its  large  amount,  is  sodium  chloride,  and  the  chief  inhibitor 
of  pulsation  is  the  magnesium.  As  is  well  known,  however,  pure 
sodium  chloride  solutions  can  not  sustain  pulsation,  for  in  all  known 
cases  of  rhythmical  movement  from  that  of  Medusae  to  that  of  the 
vertebrate  heart,  calcium  and  potassium  must  be  associated  with  the 
sodium,  and  I  find  that  magnesium  must  also  be  present  to  restrain  the 
highly  stimulating  influence  of  the  combination  of  sodium,  calcium, 
and  potassium.  Indeed,  in  order  to  pulsate  rhythmically  an  organ 
must  be  in  that  delicately  balanced  state  known  to  physiologists  as 
being  upon  the  threshold  of  stimulation.  When  in  this  condition  a 
constantly  accumulating  internal  stimulus,  which  is  reduced  at  each 
contraction,  will  maintain  rhythmical  pulsation. 

Normal  Medusae  of  Cassiopea  with  marginal  sense-organs  intact  will 
pulsate  for  a  short  time  with  abnormal  rapidity  in  a  pure  ^n  NaCl 
solution,  but  their  rate  quickly  declines  so  as  to  become  abnormally 
slow,  and  in  about  10  minutes  they  begin  to  pulsate  only  at  intervals 
with  longer  and  longer  periods  of  rest  between  periods  of  pulsation. 
Practically  all  movement  ceases  at  the  end  of  about  30  minutes.  Little 
or  no  toxic  effect  is  produced,  however,  for  recovery  is  almost  instan- 
taneous in  sea- water,  and  pulsation  can  be  revived,  even  after  several 
hours ,  by  the  addition  of  any  calcium  salt  to  the  NaCl  solution . 

Pulsation  of  normal  Cassiopea  ceases  in  i  to  6  minutes  in  a  solution 
containing  the  amounts  of  NaCl  and  MgSO4  +  MgCl2  found  in  sea- 
water,  but  it  can  sometimes  be  revived  temporarily  by  adding  potas- 
sium, or  always  by  the  amount  of  calcium  found  in  sea- water. 

Normal  Medusae  of  Cassiopea  are  but  little  affected  by  an  excess  of 
NaCl  in  the  sea-water,  and  will  pulsate  for  more  than  18  hours  in  sea- 
water  +  i  per  cent  excess  of  NaCl.  Their  pulsation,  however,  becomes 
somewhat  irregular,  although  of  practically  normal  average  rate,  but 
the  mouth-arms  are  strongly  and  abnormally  contracted.  Recovery  in 
sea- water  is,  however,  very  rapid  and  no  apparent  toxic  effects  are 
produced.  A  Medusa  in  sea-water  + 1.55  per  cent  excess  of  NaCl 
pulsates  with  abnormal  rapidity  for  half  an  hour,  and  although  shriv- 
eled, recovers  quickly  on  being  replaced  in  normal  sea- water. 


48  PUIySATlON   OF 

When  we  proportionately  reduce  the  sodium  chloride  and  mag- 
nesium, but  at  the  same  time  maintain  the  amounts  of  calcium  and 
potassium  of  the  sea- water,  the  rate  of  pulsation  and  general  energy 
of  the  Medusae  steadily  decline.  This  was  done  by  diluting  sea-water 
with  distilled  water  containing  the  amounts  of  calcium  and  potassium 
found  in  sea-water,  as  is  described  on  page  18.  If  we  simply  dilute 
the  sea-water  with  distilled  water  the  rate  of  pulsation  does  not  decline 
so  rapidly,  and  the  injurious  effects  are  not  so  pronounced. 

These  experiments  show  that  a  relative  excess  of  Ca  and  K  retards 
pulsation,  even  when  the  actual  amounts  of  Ca  and  K  are  such  as  are 
found  in  sea-water. 

Cassiopea  will  pulsate  longer  in  LiCl  +  K2SO4  +  CaSO4  than  in  a 
solution  wherein  the  NaCl  is  replaced  by  Na2CO3 .  In  these  solutions 
the  L,iCl  and  Na2CO3  were  isotonic  with  the  NaCl  of  sea- water,  while 
the  amounts  of  K  and  Ca  were  the  same  as  are  found  in  sea- water. 
The  Medusae  ceased  pulsating  in  about  6  minutes  in  the  L,iCl  solution , 
but  it  seems  somewhat  remarkable,  in  illustrating  the  effects  of  salts 
as  a  whole,  that  14 Cl  should  replace  the  NaCl  with  less  injury  than 
Na2CO3. 

We  have  seen  that  NaCl  in  excess  or  in  pure  solutions  has  very  little 
toxic  effect  upon  Cassiopea.  This  appears  remarkable,  for  its  marked 
toxic  effects  have  been  made  known  by  Loeb,  Lingle,  Gushing,  and 
others  upon  a  number  of  animals,  and  I  find  that  pure  solutions  of 
NaCl  have  a  very  rapidly  injurious  effect  upon  the  movement  of  the 
branchial  arms  of  Lepas.  We  must  remember,  however,  that  Cassiopea 
normally  lives  in  semi-stagnant  salt-water  lagoons  where  considerable 
range  in  density  must  take  place  through  evaporation  and  rainfall. 
It  is  also  one  of  the  most  hardy  of  marine  animals  and  will  survive 
without  serious  effects  several  minutes'  immersion  in  sea- water  con- 
taining such  poisons  as  o.i  per  cent  KCN. 

It  will  be  recalled  that  Macallum  (1903)  found  that  while  the  amount 
of  NaCl  in  brackish  estuaries  might  change  greatly  with  the  condition 
of  the  tide,  the  amount  of  NaCl  in  the  bodies  of  the  Aurelia  and  Cyanea 
remained  practically  constant.  It  is  therefore  possible  that  Cassiopea 
may  resist  osmosis  of  NaCl  to  some  extent  and  thus  avoid  its  possibly 
toxic  influences. 

We  conclude  that  NaCl  is  a  stimulant  and  is  counteracted  in  this 
respect  by  the  magnesium  of  sea-water  so  as  to  produce  a  balanced 
solution.  It  can  not  maintain  pulsation  except  in  connection  with 
calcium  and  potassium,  in  combination  with  which  it  forms  a  powerful 
stimulant  which  produces  a  rapid  but  only  temporary  pulsation,  mag- 
nesium being  necessary  to  reduce  and  sustain  its  action. 


INTERACTION   OF  SALTS. 


49 


ARTIFICIAL  SEA-WATER    AND  THE  EFFECTS  OF  THE  SALTS  OF  SEA- 
WATER,  AS   A   WHOLE,    UPON  PULSATION. 

In  the  experiments  upon  Cassiopea  the  solutions  containing  some  or 
all  of  the  chief  constituents  of  sea-water  were  made  up  in  accordance 
with  the  formula  given  by  Dittmar  (1884)*,  and  also  according  to 
Van  't  Hoff's  formula  (100  NaCl  +2.2  KC1  +  7.8  MgCl2  +3.8  MgSO4  + 
3  CaCl2,  all  of  ^n  concentration. 

Medusae  pulsate  normally  in  an  artificial  sea-water  made  according 
to  Van  't  Hoff's  formula,  but  pulsation  is  somewhat  irregular  in  a 
sea- water  made  according  to  Dittmar 's  formula.  Table  4  shows  the 
results  of  experiments  with  Dittmar's  formula,  and  table  5  gives  the 
results  obtained  by  using  Van  't  Hoff's  formula. 

Tables  4  and  5  show  the  effects  upon  Cassiopea  of  various  solutions 
containing  one  or  more  of  the  constituents  of  sea- water.  It  will  be 
apparent  that  magnesium  is  the  chief  restrain er  of  pulsation,  and  that 
it  prevents  the  spontaneous  contraction  of  disks  deprived  of  mar- 
ginal sense-organs  and  retards  pulsation  in  perfect  Medusae.  When 
magnesium  is  present  the  absence  of  calcium  quickly  stops  pulsation , 
but  when  magnesium  is  absent  we  may  have  calcium  also  absent  and 
the  Medusae  will  pulsate  for  a  considerable  time.  It  is  apparent, 
therefore,  that  calcium  assists  the  NaCl  to  counteract  the  retarding 
influence  of  magnesium.  This  is  also  shown  by  the  fact  that  Medusae 
pulsate  for  a  long  time  in  Na  +  Mg  +  Ca,  whereas  all  movement  ceases 
very  soon  in  Na  +  Mg. 

Potassium,  however,  does  not  assist  the  NaCl  to  resist  the  stupefy- 
ing influence  of  magnesium,  for  Medusae  cease  to  pulsate  almost  as  soon 
in  Na  +  Mg  +  K  as  they  do  in  Na  +  Mg.  Potassium  serves  mainly  to 
stimulate  movement  in  connection  with  both  calcium  and  sodium  ;  thus 
Na  +  K  and  Na  +  Ca  give  temporary  pulsations  at  about  normal  rate ; 
whereas  Na  +  Ca  +  K  gives  strong  pulsations  at  fully  twice  the  nor- 
mal rate,  but  these  can  not  be  sustained  indefinitely  unless  magnesium 
be  present  to  counteract  the  too  powerful  stimulating  effects  of  the 
Na  +  Ca  +  K.  A  Ringer's  solution  is  only  a  powerful  stimulant,  and 
can  not  sustain  pulsation  indefinitely  unless  tempered  by  magnesium. 
Potassium  has  little  power  to  revive  pulsation,  whereas  calcium  pos- 
sesses this  power  to  a  marked  degree  ;  thus,  when  pulsations  have 
ceased  in  NaCl  they  can  always  be  revived  by  calcium,  but  at  best 
only  a  very  few  isolated  contractions  can  be  revived  by  potassium  in 
the  amount  and  proportion  found  in  sea -water. 

^Reports  of  voyage  of  H.  M.  S.  Challenger,  Chemistry,  vol.  I,  p.  204. 


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continues  more  than  an  hour  with- 
out periods  of  rest. 

All  movement  ceases  in  less  than  6 
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with  activity.  Practically  all  move- 
ment dies  out  in  about  50  minutes. 

Pulsation  not  rapid. 
Periods  of  quiescence  alternating 

with  activity.  Whenever  the 
Medusa  comes  to  rest  its  mouth- 
arms  contract,  but  they  expand 
soon  after  movement  is  resumed. 

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52 


PUI^ATION   OF  JELLYFISHKS. 


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EFFECTS  OF  VAN   'T  HOFF'S  SEA-WATER. 


53 


TABLE  5. — Effects  upon  the  rhythmical  pulsation  of  Cassiopea^  exerted  by  solutions 
containing  Na,  Ca,  K,  and  Mg  in  amounts  and  proportions  found  in  sea- 
ivater  according  to  Van  '£  HofT s  formula,  wherein  sea-zuater  is  supposed  to 
contain  100  NaCl +  2.2  KCl  +  7-8  MgCl*  +  3.8  MgSOt  +  ^CaCh,  all  of  ftn 
concentration. 


Composition  of  the  solution. 


Normal  Medusae  taken  from 
sea-water  and  placed  in  the 
solution  pulsate  as  fol- 
lows : 


Disks  made  by  cutting  off 
the  marginal  sense-organs 
of  Cassiopea  behave  as 
follows  : 


NaCl 


NaCl-fCaCla 


NaCl+  KCl 


NaCl  +  MgCl2 

NaCl+MgSOi 

NaCl  +  MgCl2  +  MgSOi 


NaCl  +  MgCl2  +  MgSO4  +  KCl 


NaCl  4-   MgClg  + 
CaCl2. 


NaCl  +  MgCla  +  MgSO4+KCl 
+CaCl2. 


Pulsation  is  abnormally 
rapid  at  first,  but  in  from 
7  to  10  minutes  periods  of 
rest  appear  and  these  in- 
crease in  duration  and 
frequency  while  the  pe- 
riods of  active  pulsation 
decrease.  All  movement 
dies  put  before  the  end  of 
45  minutes. 

At  first  the  rate  is  about 
normal.  Periods  of  rest 
begin  to  appear  after  be- 
ing about  15  minutes  in 
the  solution.  These  peri- 
ods of  rest  increase  in  dur- 
ation and  frequency  so 
that  all  movement  ceases 
before  the  end  of  \%  hours. 

Pulsation  is  abnormally  rap- 
id at  first,  but  at  the  end 
of  about  half  an  hour 
pauses  set  in,  and  these 
periods  of  rest  gradually 
increase  in  length  and  fre- 
quency. All  movement 
ceases  after  the  Medusa 
has  pulsated  somewhat 
more  than  2  hours. 

Pulsation  is  maintained 
without  pauses  at  fully 
twice  the  normal  rate  for 
more  than  2  hours  ;  then 
periods  of  rest  are  apt  to 
commence.  The  Medusa 
pulsates  over  4  hours. 

Pulsation  declines  steadily 
and  ceases  before  the  end 
of  6  minutes. 

Pulsation  declines  at  once 
and  all  movement  ceases 
before  end  of  10  minutes. 

Pulsation  declines  rapidly 
and  usually  ceases  before 
the  end  of  30  seconds. 
Some  Medusae  may  pulsate 
longer  than  5  but  less  than 
6  minutes.  It  is  restored 
if  we  add  CaCl2,  but  not 
usually  by  KCl, 

Pulsation  steadily  declines 
and  ceases  before  the  end 
of  6  minutes.  It  is  effectu- 
ally restored  by  adding 
CaCl2. 

Rate  normal  at  first  but  de- 
clines slowly  with  pauses, 
so  that  all  movement 
ceases  before  the  end  of  40 
minutes.  Pulsation  is  re- 
stored by  adding  KCl. 

Pulsation  is  normal  as  in 
natural  sea-water. 


Newly  cut  disks  give  a  few 
contractions,  then  subside 
into  quiescence.  Disks 
two  or  more  days  old  usu- 
ally pulsate  slowly  and  ir- 
regularly for  hours. 


Disks  behave  very  much  as 
they  do  in  NaCl,  but  are 
somewhat  more  actively 
stimulated. 


Disks  behave  as  they  do  in 
NaCl+CaCl2,  but  are  more 
strongly  stimulated. 


Disks  are  powerfully  stimu- 
lated, and  even  newly 
made  disks  may  com- 
mence spontaneous,  irreg- 
lar  pulsation  which  may 
continue  for  several  hours. 

No  pulsation. 


No  pulsation. 
No  pulsation. 


No  pulsation  occurs. 


No  pulsation. 


Newly   made  disks  do  not 

Sulsate.    Disks  2  or  more 
ays  old  pulsate  irregular- 
ly- 


54  PULSATION   IN   BARNACLE,   TUNICATE,   AND  TURTLE. 


IV.    PULSATION  OF  THE  BRANCHIAL  ARMS  OF  LEPAS,  THE  HEART 
OF  SALPA,  AND  THE  HEART  OF  THE  LOGGERHEAD  TURTLE. 

The  Medusae  are  the  most  primitive  of  the  raetazoans  which  display 
rhythmical  pulsation,  and  therefore  a  study  of  the  laws  which  control 
their  movement  is  important,  for  it  is  practically  certain  that  pulsation 
began  to  attain  physiological  importance  in  primitive  marine  animals, 
and  that  the  vertebrate  heart ,  developed  in  creatures  living  in  salt 
water.  In  the  most  primitive  forms  the  body  pulsates  as  a  whole,  but 
finally  pulsation  is  assumed  by  or  restricted  to  special  organs.  It  is 
therefore  interesting  to  consider  various  sorts  of  pulsating  organs  in 
order  to  see  whether  some  fundamental  conditions  may  not  apply  to 
all  of  them. 

Accordingly  studies  were  made  of  the  pulsation  of  the  heart  of  the 
solitary  asexual  form  of  Salpa  democratica,  the  rhythmical  move- 
ment of  the  branchial  arms  of  Lepas,  and  the  pulsation  of  the  heart  of 
the  embryo  loggerhead  turtle,  Thalassochelys  caret ta,  and  these  varied 
sorts  of  pulsation  were  compared  with  that  of  the  jellyfish  Cassiopea. 

The  results  are  presented  in  condensed  form  in  table  6  (p.  60)  which 
shows  the  number  of  minutes  that  pulsation  endures  in  various  solu- 
tions consisting  of  one  or  all  of  the  ingredients  Nad,  KC1,  CaCl2, 
MgSO4,  and  MgCl2.  In  the  experiments  upon  Cassiopea,  Lepas,  and 
Salpa  Van  t'  HofF's  sea- water  solution  was  employed.  This  con- 
sists of  100  NaCl  4-  2.2  KC1  +  7.8  MgCl2  +  3.8  MgSO4  +  3CaCl2,  all  of 
y%n  concentration.  In  experiments  upon  the  heart  of  the  logger- 
head turtle  the  proportions  of  the  above-named  salts  were  changed  so 
as  to  be  o.  7  per  cent  NaCl  +  0.03  per  cent  KC1  +  o.i  per  cent  MgCl2  + 
0.025  per  cent  CaCl2.  The  various  animals  were  placed  in  solutions 
containing  one  or  all  of  these  salts  in  the  amounts  and  proportions 
stated  above.  Where  +  follows  a  number  it  means  that  pulsation  occa- 
sionally lasts  a  few  more  minutes  than  is  here  recorded,  and  on  the 
other  hand,  —  following  a  number  means  that  the  pulsation  does  not 
usually  last  as  long  as  is  recorded. 

An  inspection  of  table  6  (p.  60)  will  show  that  pulsation  in  all  of 
theselforms  (jellyfish,  barnacle,  tunicate,  and  reptile)  is  most  powerfully 
stimulated  by  solutions  composed  of  sodium  chloride,  potassium,  and 
calcium,  and  that  all  are  depressed  by  magnesium.  Nevertheless 
sustained  pulsation  can  only  take  place  in  a  solution  containing 
sodium,  potassium,  calcium,  and  magnesium,  the  last-named  element 
being  necessary  to  "  tone  down"  and  restrain  the  strong  stimulation 
caused  by  the  first  three,  thus  giving  a  slower  but  indefinitely  sus- 
tained pulsation.  This  important  r61e  of  magnesium  has  hitherto 


BARNACLE,   TUNICATE,   AND  TURTLE.  55 

been  unsuspected,  and  we  see  that  Ringer's  solutions,  which  consist  of 
combinations  of  sodium,  potassium,  and  calcium  chlorides,  are  only 
stimulants,  and  must  be  partially  inhibited  and  restrained  by  mag- 
nesium in  order  that  they  may  sustain  pulsation  indefinitely. 

In  simple  marine  animals  such  as  Medusae,  barnacles,  and  Salpa  the 
optimum  solution  for  pulsation  is  the  sea-water  itself,  but  in  the  higher 
terrestrial  forms  the  proportions  and  amounts  of  the  ingredients  of  the 
optimum  solution  have  changed,  although  still  composed  of  sodium 
chloride,  potassium,  calcium,  and  magnesium.  In  Cassiopea,  Lepas, 
and  Salpa  it  is  the  special  r61e  of  calcium  to  assist  the  sodium  chloride 
to  overcome  the  anesthetic  effect  of  magnesium,  whereas  potassium 
practically  lacks  this  power. 

A  further  inspection  of  table  6  shows  that  there  are  considerable 
differences  in  the  effects  of  various  elements  upon  different  animals. 
For  example,  pulsation  is  sustained  fairly  well  in  Cassiopea,  the  heart 
of  Salpa  democratica,  and  the  loggerhead  turtle  embryo  by  a  pure 
NaCl  solution,  but  this  quickly  stops  the  movement  of  the  branchial 
arms  of  Lepas.  Also,  the  addition  of  KC1  to  NaCl  greatly  improves 
the  solution  in  its  ability  to  sustain  the  pulsation  of  Cassiopea,  whereas 
it  has  but  little  beneficial  effect  in  the  case  of  the  arms  of  Lepas.  Cal- 
cium, on  the  other  hand,  has  but  little  power  to  sustain  pulsation  in 
connection  with  NaCl  in  Cassiopea,  but  in  the  case  of  the  arms  of  Lepas 
it  is  very  efficient.  In  Cassiopea  pulsation  ceases  almost  instantly  in 
such  non-ionizable  solutions  as  urea,  dextrose,  and  glycerin,  but  the 
heart  of  Salpa  democratica  will  pulsate  for  a  considerable  time  in  these 
solutions,  and  the  heart  of  the  embryo  loggerhead  turtle  pulsates  as 
long  in  dextrose  as  it  does  in  NaCl.  These  differences  in  the  effects 
of  the  several  salts  upon  pulsation  in  different  animals  are  so  consider- 
able that  we  must  be  cautious  of  drawing  general  conclusions  from 
the  behavior  of  any  one  animal  and  applying  them  to  related  forms. 
For  example,  Cassiopea  can  not  pulsate  for  6  minutes  in  a  solution 
resembling  sea- water  but  simply  lacking  calcium,  whereas  another 
Scyphomedusa,  Linerges  mercurius,  will  pulsate  for  45  minutes  in  the 
same  solution.  Both  Linerges  and  Cassiopea  are,  however,  restored  to 
normal  pulsation  by  the  addition  of  calcium,  and  the  difference  in 
their  behavior  is  one  of  degree,  not  of  kind.  The  papers  of  physiol- 
ogists abound  in  general  conclusions  concerning  the  action  of  "the 
vertebrate  heart ' '  when  only  the  heart  of  the  terrapin  or  the  dog  has 
been  studied,  and  undoubtedly  these  sweeping  conclusions  are  often 
misleading.  For  example,  when  the  loggerhead  turtle  embryo  is  1 1  to 
14  days  old  its  heart  ceases  to  pulsate  in  less  than  22  minutes  in  the 


56  HEART  OF  LOGGERHEAD  TURTLE. 

albumen  of  its  own  egg,  but  when  it  is  41  days  old  it  pulsates  from  3 
to  7  hours  in  the  albumen  of  its  egg,  which  then  sustains  it  better  than 
can  a  Ringer's  solution,  or  any  solution  I  could  devise.  The  albu- 
men contains  Na,  K,  Ca,  and  Mg. 


Fig.  34. — Showing  the  decline  in  rate  and  also  the  length  of  time  that  pulsation 
endured  in  the  hearts  of  10  loggerhead  turtle  embryos  (11  to  14  days  old) 
placed  in  0.7  per  cent  NaCl-j-0. 1  per  cent  MgCl2.  The  heavy  dark  line  shows 
the  average  condition,  and  the  fine  full  lines  show  the  behavior  of  individual 
embryos.  The  dotted  lines  cover  periods  from  the  last  observation  to  the  time 
when  the  heart  ceased  to  beat. 

The  ' '  all  or  none  ' '  principle  in  pulsation  does  not  apply  to  the  pul- 
sation of  the  heart  of  the  embryo  loggerhead  turtle,  for  the  ventricle 
ceases  first,  then  after  a  long  time  the  auricles  cease  to  pulsate,  but 
the  sinus  still  pulsates.  Normally,  as  is  well  known,  the  heart-beat 
originates  in  the  sinus;  then  after  an  interval  the  auricles  respond, 
and  finally  the  ventricle  contracts.  After  the  heart  which  has  been 
removed  from  the  body  has  ceased  to  pulsate,  however,  we  may  stim- 


HEART  OF  TURTLE. 


57 


ulatethe  ventricle  by  an  induction  current,  and  after  the  current  has 
been  removed  the  heart  may  pulsate  for  several  minutes  in  a  reverse 
manner,  each  contraction  originating  at  the  stimulated  place  in  the  ven- 
tricle, then  after  a  pause  the  auricles,  and  finally  the  sinus  contracting. 


60 


50 


20 


3O 

MINUTES 


60 


Fig.  35.— The  full  heavy  line  shows  the  average  rate  and  duration  of  pulsation  of 
the  hearts  of  10  loggerhead  turtle  embryos  (11  to  14  days  old)  in  0.7  per  cent 
NaCl.  The  dotted  line  shows  the  same  things  for  the  hearts  of  10  embryos  in 
0.7  per  cent  NaCl+0. 1  per  cent  MgCl2 .  It  appears  that  the  NaCl+  MgCl2  does 
not  affect  the  rate,  but  nevertheless  it  stops  the  heart  sooner  than  does  the  pure 
NaCl  solution. 

The  heart  of  the  loggerhead  turtle  often  revives  temporarily  im- 
mediately before  it  ceases  to  pulsate  in  solutions.  This  is  seen  in 
figures  34  and  36,  which  show  the  decrease  in  the  rates  of  pulsation  of 
the  hearts  of  20  loggerhead  turtle  embryos  n  to  14  days  old.  Ten  of 
these  (fig.  36)  were  placed  in  0.7  per  cent  NaCl,  and  10  others 
whose  pulsation  is  shown  in  figure  34  were  placed  in  0.7  per  cent 
NaCl+o.i  per  cent  MgCl2.  The  MgCl2  has  no  effect  upon  the  rate, 
but  it  stops  the  heart  sooner  than  does  the  pure  NaCl.  (See  fig.  35-) 

After  the  heart  of  the  loggerhead  turtle  has  ceased  to  pulsate  m 
NaCl  it  may  be  revived  temporarily  by  CaCl2.  KC1  will  also  revive 


58  PUPATION    OF  TURTLE'S   HEART. 

it,  but  not  so  powerfully,  and  even  distilled  water  or  MgCl2  will  often 
give  rise  to  a  few  final,  weak  pulsations.  In  other  words,  the  heart 
responds  to  any  osmotic  change,  be  it  beneficial  or  injurious.  It  is 
worthy  of  note,  however,  that  if  the  heart  ceases  to  beat  in  NaCl  + 
MgCl2  it  is  usually  impossible  to  revive  it,  even  by  CaCl2. 

The  heart  of  the  loggerhead  turtle  embryo,  14  days  old,  pulsates 
more  rapidly,  and  usually  longer,  in  0.7  per  cent  NaCl +0.03  per 
cent  KC1  than  it  does  in  0.7  per  cent  NaCl.  Thus  the  addition  of  a 
small  amount  of  KC1  acts  as  a  stimulus.  Physiologists  are  in  dispute 
concerning  the  action  of  potassium  upon  the  "  vertebrate  heart,"  the 
general  opinion  being  that  potassium  depresses  the  heart.  The  litera- 
ture of  this  subject  is  reviewed  by  Carlson  (1906,  Amer.  Journ.  Phys- 
iology, vol.  16,  p.  397).  Much  of  the  discrepancy  in  results  arises 
from  the  sweeping  conclusions  which  physiologists  have  drawn  in 
applying  to  all  vertebrates  the  results  achieved  from  experiments 
upon  a  few  forms.  Moreover,  in  some  papers  experiments  are  con- 
ducted upon  each  salt  separately,  and  the  assumption  is  made  that 
the  effect  of  a  mixture  of  these  salts  is  merely  the  summation  of  their 
individual  effects.  Nothing  could  be  more  erroneous.  For  example, 
calcium  alone  never  stimulates,  but  even  inhibits  pulsation  in  Cassi- 
opea,  but  in  connection  with  sodium  and  potassium  chlorides  it  forms  a 
most  powerful  stimulant. 

In  closing  we  will  state  that  the  heart  of  the  embryo  loggerhead  tur- 
tle behaves  quite  differently  from  that  of  the  animal  after  hatching,  but 
we  will  leave  the  discussion  of  this  and  other  points  to  a  future  paper, 
wherein  we  hope  to  treat  of  the  general  effects  of  different  salts  upon 
the  hearts  of  various  vertebrates  and  invertebrates. 

In  conclusion  it  may  be  said  that  rhythmical  pulsation  can  be  sus- 
tained only  when  an  external  stimulant  is  counteracted  by  an  inhibi- 
tor, so  that  the  pulsating  organism  is  in  a  state  bordering  upon  the 
threshold  of  stimulation.  This  allows  the  weakest  internal  stimuli  to 
produce  periodic  contractions.  Each  contraction  either  produces  a 
chemical  change  which  periodically  reduces  the  internal  stimulus,  or 
the  tissue  can  not  again  respond  to  the  ever-present,  constant  stimulus 
until  after  a  period  of  rest. 


PUPATION   OF  TURTLE'S  HEART. 
PULSATIONS  PER  MINUTE 


59 


Fig.  36.-Showing  the  decline  in  rate  and  also  the  length  of  time  that  pulsation  lasted  in  the 
hearts  of  10  loggerhead  turtle  embryos  (11  to  14  days  old)  placed  in  0.7  per  cent  Nad  The 
heavy  line  shows  the  average  condition,  and  the  fine  unbroken  lines  show  behavior  of  individual 
embryos  numbered  from  1  to  10.  The  dotted  lines  cover  periods  from  the  last  observation  to 
the  time  when  the  heart  ceased  to  beat. 


60 


DURATION   OF   PUI^SATION   IN   SOLUTION. 


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PAPERS  CITED.  6 1 

LITERATURE. 


BANCROFT,  F.  W.     1904.     Note  on  the  galvanotropic  reaction  of  the  Medusa  Polyor- 

chis  $enicillata  A.  Agassiz.    Journ.  Experimental  Zool.,  vol.  i,  No.  2  pp  280- 

292. 
BANCROFT   F.  W.,  and  ESTERLY,  C.  O.     1903.     A  case  of  physiological  polarization 

of  the  Ascidian  heart.     Univ.  of  California  Publications,  Zool.,  vol    i    po 

105-114. 

BETHE,  A.  1903.  Allgemeine  Anatomic  und  Physiologie  des  Nervensystems  Leip- 
zig, 487  pp. 

BIGELOW,  R.  P.  1892.  Cassiopea  xamachana,  in  Zool.  Anzeiger.  Bd.  xv.,  p.  212 
Also  Mem.  Boston  Soc.  Nat.  Hist.,  1900,  vol.  v,  No.  6,  pp.  191-236.  ' 

CARLSON,  A.  J.  1904.  The  nervous  origin  of  the  heart-beat  in  Limulus,  and  the 
nervous  nature  of  co-ordination  or  conduction  in  the  heart.  American  Jour. 
Physiol.,  vol.  xii,  pp.  67-74.  Also  many  papers  in  same  journal,  1904-1906. 

1906.     On  the  chemical  conditions  for  the  heart  activity,  with  special  refer- 
ence to  the  heart  of  Limulus.    American  Journal  of  Physiology,  vol  xvi  No 
3,  pp.  378-408. 

GUSHING,  H.  1901.  Concerning  the  poisonous  effect  of  pure  sodium  chloride  solu- 
tions upon  the  nerve-muscle  preparation.  Amer.  Journ.  Physiol  vol  vi  pp 
77-90. 

DITTMAR,  W.  1884.  The  composition  of  ocean  water.  Reports  of  Voyage  H.  M.  S. 
Challenger.  Chemistry,  vol.  i,  p.  204. 

EIMER,  TH.  1874.  Uber  kunstliche  Theilbarkeit  von  Aurelia  aurita  und  Cyanea 
ca^illate  in  physiologische  Individuen.  Verhandl.  physik — Medic.  Gesell- 
schaft,  Wiirzburg.  N.  F.  Bd.  vi.  Also,  1878  ;  Die  Medusen  physiologisch 
und  morphologisch  auf  ihr  Nervensystem  untersucht.  Tubingen. 

FEWKES,  J.  W.  1882.  Cassiopea.  Bull.  Mus.  Comp.  Zool.  at  Harvard  Coll.,  vol. 
ix,  p.  254.  Also,  1883,  ibid.,  vol.  xi,  p.  80. 

GASKELL,  W,  H.  1900.  The  contraction  of  cardiac  muscle,  in  Schafer's  Text-Book 
of  Physiology,  vol.  n,  pp.  169-227.  Edinburgh  and  London. 

GREENE,  C.  W.  1898.  On  the  relation  of  the  inorganic  salts  of  the  blood  to  the 
automatic  activity  of  a  strip  of  ventricular  muscle.  American  Journ.  Phys- 
iol. vol.  n,  pp.  82-126. 

HARGITT,  C.  W.  1899.  Experimental  studies  upon  Hydromedusae.  Biol.  Bulletin, 
Boston,  vol.  i,  No.  i,  pp.  35-51.  Also,  1904,  Regeneration  in  Rhizostoma 
jbulmo,  Journal  of  Experimental  Zoology,  vol.  i,  No.  i,  pp.  73-94. 

HESSE,  R.  1895.  Uber  das  Nervensystem  und  die  Sinnesorgane  von  Rhizostoma 
cuvieri.  Zeitsch  fur  Wissen.  Zoologie,  Bd.  60,  pp.  411-556,  Taf.  20-22. 

HOWELL,  W.  H.  1898.  On  the  relation  of  the  blood  to  the  automaticity  and  sequence 
of  the  heart-beat.  American  Journ.  Physiol.,  vol.  n,  pp.  47-81. 

1901.     An  analysis    of  the  influence  of  the  sodium,  potassium,   and  calcium 

salts  of  the  blood  on  the  automatic  contractions  of   heart  muscle.    American 
Journ.  Physiol.,  vol.  vi,  pp.  181-206. 

1906.     Text-Book  of  Physiology,   pp.    477-530.     Philadelphia   and    London. 

LINGLE,  D.    J.     1900.     The  action  of  certain  ions  on  ventricular  muscle.     American 

Journal  of  Physiology,  vol.  iv,  pp.  265-282. 

LOEB,  J.  1899.  Ueber  lonen  welche  rhythmische  zuckungen  der  Skelettmuskeln 
hervorrufen.  Festschrift  fur  Fick.  Braunschweig. 

1900.  On  ion-proteid  compounds  and  their  role  in  the  mechanics  of  life  phe- 
nomena, etc.  American  Journ.  Physiol.,  vol.  in,  pp.  327—338. 

LOEB,  J.  1900.  On  the  different  effects  of  ions  upon  myogenic  and  neurogenic  rhyth- 
mical contractions,  and  upon  embryonic  and  muscular  tissue.  American- 
Journ.  Physiol.,  vol.  in,  pp.  383-396. 

1905.  Studies  in  General  Physiology,  2  vols.,  782  pp.  Decennial  Publica- 
tions, University  of  Chicago. 

1906.     The  stimulating  and  inhibitory  effects  of  magnesium  and  calcium  upon 

the  rhythmical  contractions  of  a  jelly-fish  (Polyorchis).     Journ.  of  Biological 
Chemistry,  New  York,  vol.  i,  No.  6,  pp.  427-436. 

MACALLUM,  A.  B.  1903.  The  inorganic  composition  of  the  Medusae  Aurelia  flavi- 
dula  and  Cyanea  arctica.  Journal  of  Physiology,  Cambridge,  England,  vol. 
29,  pp.  213-241. 


62  PAPERS  CITED. 

MATTHEWS,  A.  P.  1905.  The  toxic  and  antitoxic  action  of  salts.  Amer.  Journ. 
Physiology,  vol.  12,  pp.  419-443. 

MAYER,  A.  G.  1906.  Preliminary  report  upon  the  rhythmical  pulsation  of  Scypho- 
medusae.  Year  Book  of  the  Carnegie  Institution  of  Washington  for  1905, 
No.  4,  pp.  120-123. 

MELTZER,  S.  J.,  and  AUER,  J.  1905- '06.  Physiological  and  pharmacological  studies 
of  magnesium  salts.  I.  General  anaesthesia  by  subcutaneous  injections, 
American  Journ.  Physiol.,  vol.  xiv,  pp,  366-388.  II.  The  toxicity  of  intra- 
venous injections,  etc.  Ibid.,  vol.  xv,  pp.  385-405.  III.  The  narcotizing 
effect  of  magnesium  salts  upon  nerve  fibers.  Ibid.,  vol.  xvi,  pp.  233-251. 

MERUNOWICZ,  J.  1875.  Ueber  die  chemischen  Bedingungen  fur  die  Enstelburg  der 
Herzschlages.  Math.  Phys.  Ber.,  Leipzig,  Bd.  22,  pp.  252-298. 

MURBACH,  L.  1903.  The  static  function  in  Gonionemus.  American  Journ.  Physiol., 
vol.  x,  pp.  201-209. 

NAGEL,  W.  A.  1894.  Experimentelle  sinnesphysiologische  Untersuchungen  an 
Coelenteraten.  Pfliiger's  Archiv  fur  die  gesammte  Physiol.,  Bd.  57,  pp.  495- 
552,  Taf  7  ;  also,  Bd.  58,  p.  308. 

PORTER,  W.  T.  1898.  A  new  method  for  the  study  of  the  isolated  mammalian 
heart.  Amer.  Journ.  Physiology,  vol.  i,  pp.  511-518.  Also  1897,  Journal 
of  Experimental  Medicine,  vol.  2,  p.  391. 

RINGER,  S.  1883.  A  further  contribution  regarding  the  influence  of  the  different 
constituents  of  the  blood  on  the  contraction  of  the  heart.  Journal  of  Physi- 
ology, Cambridge,  England,  vol.  iv,  pp.  29-42,  pi.  i. 

ROGERS,  C.  G.  1905.  The  effect  of  various  salts  upon  the  survival  of  the  invertebrate 
heart.  Journ.  of  Experimental  Zool.,  vol.  n,  No.  2,  pp.  237-252,  i  plate. 

ROMANES,  G.  J.  1885.  Jelly-fish,  star-fish,  and  sea-urchins,  being  a  research  on  prim- 
itive nervous  systems.  International  Scientific  Series,  vol.  XLIX,  New  York. 
(This  is  mainly  a  review  of  the  author's  previous  papers  in  Nature,  1875,  vol. 
n,  p.  29;  Philosophical  Trans.  Royal  Soc.  London,  vols.  166,  167,  and 
171,  etc.) 

TULLBERG,  T.  1892.  Sur  la  conservation  des  invertebres  a  1'etat  d'  epanouisse- 
ment.  Archiv.  Zool.  Exper.  et  Gen.,  Tome  10,  p.  xi-xiv.  Also  Journal 
of  the  Royal  Microscopical  Society,  ser.  2,  vol.  12,  1892,  p.  435. 

VON  UEXKULL,  J.  1901.  Die  Schwimmbewegungen  von  Rhizostoma  pulmo,  Mitth. 
Zool.  Stat.  Neapel,  Bd.  xiv,  pp.  620-626. 

1904.  Die  ersten  Ursachen  der  Rythmus  in  der  Tierreihe.  Ergebnisse  der 

Physiologic,  Jahrg.,  3,  iv,  Abt.  2,  pp.  i-n. 

YERKES,  R.  M.  1902.  A  contribution  to  the  physiology  of  the  nervous  system  of 
Gonionemus  murbachii.  Part  I,  The  sensory  reaction  of  Gonionemus. 
American  Journ.  of  Physiol.,  vol.  vi,  No.  6,  pp.  434-449. 


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